Table of Contents

SUMMARY

        This summary highlights selected information from this joint proxy statement/prospectus. It may not contain all of the information that is important to you. We urge you to read carefully the entire joint proxy statement/prospectus, including the annexes, and the other documents to which we refer in order to fully understand the merger. See "Where You Can Find More Information." Each item in this summary refers to the page of this joint proxy statement/prospectus on which that subject is discussed in more detail.

In the Merger, Sterling Common Shareholders Will Receive Cash and Shares of Umpqua Common Stock (page 118)

        Umpqua and Sterling are proposing a strategic merger. If the merger is completed, Sterling common shareholders will receive 1.671 shares of Umpqua common stock and $2.18 in cash, without interest, for each share of Sterling common stock they hold immediately prior to the effective time of the merger. Umpqua will not issue any fractional shares of Umpqua common stock in the merger. Sterling shareholders who would otherwise be entitled to a fraction of a share of Umpqua common stock upon the completion of the merger will instead receive, for the fraction of a share, an amount in cash based on the Umpqua closing price. For example, if you hold 100 shares of Sterling common stock, you will receive 167 shares of Umpqua common stock and a cash payment instead of the additional 0.1 shares of Umpqua common stock that you otherwise would have received (100 shares × 1.671 = 167.1 shares) in addition to receiving $218 in cash, representing the cash portion of the merger consideration (100 shares × $2.18 = $218).

        Umpqua common stock is listed on the NASDAQ Global Select Market under the symbol "UMPQ," and Sterling common stock is listed on the NASDAQ Capital Market under the symbol "STSA." The following table shows the closing sale prices of Umpqua common stock and Sterling common stock as reported on the NASDAQ Global Select Market and NASDAQ Capital Market, respectively, on August 30, 2013, the last trading day before the press reported that Sterling was seeking takeover bids, September 10, 2013, the last full trading day before the public announcement of the merger agreement, and on January 17, 2014, the last practicable trading day before the date of this joint proxy statement/prospectus. This table also shows the implied value of the merger consideration payable for each share of Sterling common stock, which we calculated by multiplying the closing price of Umpqua common stock on those dates by the exchange ratio of 1.671 and adding the cash portion of the merger consideration of $2.18 per share.

        The merger agreement governs the merger. The merger agreement is included in this joint proxy statement/prospectus as Annex A. All descriptions in this summary and elsewhere in this joint proxy statement/prospectus of the terms and conditions of the merger are qualified by reference to the merger agreement. Please read the merger agreement carefully for a more complete understanding of the merger.

Umpqua's Board of Directors Unanimously Recommends that Umpqua Shareholders Vote "FOR" the Umpqua Merger Proposal and the Other Proposals Presented at the Umpqua Special Meeting (page 56)

        Umpqua's board of directors has determined that the merger, the merger agreement and the transactions contemplated by the merger agreement are in the best interests of Umpqua and its shareholders and has unanimously approved and adopted the merger agreement. Umpqua's board of directors unanimously recommends that Umpqua shareholders vote "FOR" the Umpqua merger proposal and "FOR" the other proposals presented at the Umpqua special meeting. For the factors considered by Umpqua's board of directors in reaching its decision to approve and adopt the merger agreement, see "The Merger—Umpqua's Reasons for the Merger; Recommendation of Umpqua's Board of Directors."

Sterling's Board of Directors Unanimously Recommends that Sterling Shareholders Vote "FOR" the Sterling Merger Proposal and the Other Proposals Presented at the Sterling Special Meeting (page 71)

        Sterling's board of directors has determined that the merger, the merger agreement and the transactions contemplated by the merger agreement are in the best interests of Sterling and its shareholders and has unanimously approved and adopted the merger agreement. Sterling's board of directors unanimously recommends that Sterling shareholders vote "FOR" the Sterling merger proposal and "FOR" the other proposals presented at the Sterling special meeting. For the factors considered by Sterling's board of directors in reaching its decision to approve and adopt the merger agreement, see "The Merger—Sterling's Reasons for the Merger; Recommendation of Sterling's Board of Directors".

Opinion of Sterling's Financial Advisor (page 74 and Annex D)

Opinion of Sandler O'Neill

        In connection with its consideration of the merger, on September 11, 2013, the Sterling board of directors received from Sandler O'Neill + Partners, L.P., Sterling's financial advisor (which we refer to as "Sandler O'Neill"), its oral opinion, which opinion was confirmed by delivery of a written opinion, dated September 11, 2013, to the effect that, as of such date and based upon and subject to the various factors, assumptions and limitations set forth in its opinion, the merger consideration in the merger was fair, from a financial point of view, to the holders of Sterling common stock. The full text of Sandler O'Neill's written opinion is attached as Annex D to this joint proxy statement/prospectus. You should read the entire opinion for a discussion of, among other things, the assumptions made, procedures followed, matters considered and limitations on the review undertaken by Sandler O'Neill in rendering its opinion. Sandler O'Neill's written opinion is addressed to the Sterling board of directors, is directed only to the merger consideration in the merger and does not constitute a recommendation to any Sterling shareholder as to how such shareholder should vote with respect to the merger or any other matter.

        For further information, see "The Merger—Opinion of Sandler O'Neill."

Opinion of Umpqua's Financial Advisor (page 90 and Annex E)

Opinion of J.P. Morgan

        In connection with the merger, J.P. Morgan Securities LLC (which we refer to as "J.P. Morgan"), Umpqua's financial advisor, delivered to Umpqua's board of directors a written opinion, dated September 10, 2013, as to the fairness to Umpqua, from a financial point of view and as of the date of the opinion, of the merger consideration provided for in the merger. The full text of the written opinion, dated September 10, 2013, of J.P. Morgan, which sets forth, among other things, the

assumptions made, procedures followed, matters considered and limitations on the review undertaken, is attached as Annex E to this joint proxy statement/prospectus. J.P. Morgan's written opinion is addressed to the Umpqua board of directors, is directed only to the merger consideration in the merger and does not constitute a recommendation to any Umpqua shareholder as to how such shareholder should vote with respect to the merger or any other matter.

        For further information, see "The Merger—Opinion of J.P. Morgan."

What Holders of Sterling Stock Options and Restricted Stock Units Will Receive (page 119)

        Stock Options.    At the effective time of the merger, each option to purchase shares of Sterling common stock outstanding immediately prior to the effective time (except for certain options with an exercise price significantly in excess of the value of the merger consideration, which Sterling will use commercially reasonable efforts to cancel prior to the effective time), will be converted into an option to purchase Umpqua common stock on the same terms and conditions as were applicable prior to the merger (taking into account that, except for new equity award compensation granted prior to the effective time of the merger, the consummation of the merger and its related transactions will constitute the first trigger under equity awards that provide for "double trigger" acceleration of vesting), except that (1) the number of shares of Umpqua common stock subject to the new option will be equal to the product of the number of shares of Sterling common stock subject to the existing option and the ratio that expresses the merger consideration solely in shares of Umpqua common stock, with the cash portion of the merger consideration converted into shares based on the Umpqua closing price (which we refer to as the "equity exchange ratio") (rounding fractional shares down to the nearest whole share), and (2) the exercise price per share of Umpqua common stock under the new option will be equal to the exercise price per share of Sterling common stock of the existing option divided by the equity exchange ratio (rounded up to the nearest whole cent).

        Restricted Stock Units.    At the effective time of the merger, each restricted stock unit in respect of Sterling common stock outstanding immediately prior to the effective time will be converted into a restricted stock unit with respect to a number of shares of Umpqua common stock equal to the product of the number of shares of Sterling common stock subject to the Sterling restricted stock unit and the equity exchange ratio, on the same terms and conditions as were applicable prior to the merger (taking into account that, except for new equity award compensation granted prior to the effective time of the merger, the consummation of the merger and its related transactions will constitute the first trigger under equity awards that provide for "double trigger" acceleration of vesting).

Umpqua Will Hold its Special Meeting on February 25, 2014 (page 56)

        The special meeting of Umpqua shareholders will be held on February 25, 2014, at 6:00 p.m. local time, at the River Place Hotel, 1510 SW Harbor Way, Portland, Oregon. At the special meeting, Umpqua shareholders will be asked to:

•

approve the Umpqua merger proposal;



•

approve the articles amendment proposal; and



•

approve the Umpqua adjournment proposal, if necessary or appropriate.

        Only holders of record of Umpqua common stock at the close of business on January 15, 2014 will be entitled to vote at the special meeting. Each share of Umpqua common stock is entitled to one vote on each proposal to be considered at the Umpqua special meeting. As of the record date, there were 112,001,584 shares of Umpqua common stock entitled to vote at the special meeting. As of the record date, the directors and executive officers of Umpqua and their affiliates beneficially owned and were entitled to vote approximately 1,213,226 shares of Umpqua common stock representing approximately 1.1% of the shares of Umpqua common stock outstanding on that date.

        To approve the Umpqua merger proposal, a majority of the shares of Umpqua common stock outstanding and entitled to vote thereon must be voted in favor of such proposal. To approve the Umpqua adjournment proposal, a majority of the shares of Umpqua common stock represented at the special meeting must be voted in favor of the proposal. The articles amendment proposal will be approved if the votes cast in favor of the proposal at the Umpqua special meeting exceed the votes cast in opposition. If you mark "ABSTAIN" on your proxy card, fail to either submit a proxy or vote by telephone or internet or in person at the Umpqua special meeting or fail to instruct your bank or broker how to vote with respect to the Umpqua merger proposal, it will have the same effect as a vote "AGAINST" the proposal. If you mark "ABSTAIN" on your proxy card, or fail to instruct your bank or broker how to vote, with respect to the Umpqua adjournment proposal, it will have the same effect as a vote "AGAINST" the proposal. If, however, you are not a "street name" holder and fail to either submit a proxy card entirely or vote by telephone or internet or in person at the Umpqua special meeting, it will have no effect on such proposal. If you mark "ABSTAIN" on your proxy card, fail to either submit a proxy or vote by telephone or internet or in person at the Umpqua special meeting or fail to instruct your bank or broker how to vote with respect to the articles amendment proposal, it will have no effect on the proposal.

Sterling Will Hold its Special Meeting on February 25, 2014 (page 51)

        The special meeting of Sterling shareholders will be held on February 25, 2014, at 3:00 p.m. local time, at Sterling Bank, 111 North Wall Street, Spokane, Washington. At the special meeting, Sterling shareholders will be asked to:

•

approve the Sterling merger proposal;



•

approve the Sterling compensation proposal; and



•

approve the Sterling adjournment proposal, if necessary or appropriate.

        Only holders of record of Sterling common stock at the close of business on January 15, 2014 will be entitled to vote at the special meeting. Each share of Sterling common stock is entitled to one vote on each proposal to be considered at the Sterling special meeting. As of the record date, there were 62,363,741 shares of Sterling common stock entitled to vote at the special meeting. As of the record date, and including shares owned by Warburg Pincus and shares owned by THL, the directors and executive officers of Sterling and their affiliates beneficially owned and were entitled to vote approximately 26,978,796 shares of Sterling common stock representing approximately 43.3% of the shares of Sterling common stock outstanding on that date. Warburg Pincus and THL, each of which is associated with one of Sterling's directors and as of the record date had the right to vote approximately 12,950,796, or approximately 20.8%, of the outstanding shares of Sterling common stock, have agreed, subject to certain exceptions, to vote their shares of Sterling common stock in favor of the Sterling merger proposal. For further information, see "The Merger—Investor Letter Agreements."

        To approve the Sterling merger proposal, two-thirds of the shares of Sterling common stock outstanding and entitled to vote thereon must be voted in favor of such proposal. The Sterling compensation proposal will be approved if the votes cast in favor of such proposal at the Sterling special meeting exceed the votes cast in opposition. To approve the Sterling adjournment proposal, a majority of the shares of Sterling common stock represented at the special meeting must be voted in favor of the proposal. If you mark "ABSTAIN" on your proxy card, fail to submit a proxy or vote by telephone or internet or in person at the Sterling special meeting or fail to instruct your bank or broker how to vote with respect to the Sterling merger proposal, it will have the same effect as a vote "AGAINST" the proposal. If you mark "ABSTAIN" on your proxy card, fail to submit a proxy or vote by telephone or internet or in person at the Sterling special meeting or fail to instruct your bank or broker how to vote with respect to the Sterling compensation proposal, it will have no effect on the proposal. If you mark "ABSTAIN" on your proxy card, or fail to instruct your bank or broker how to

vote, with respect to the Sterling adjournment proposal, it will have the same effect as a vote "AGAINST" the proposal. If, however, you are not a "street name" holder and fail to submit a proxy card entirely or vote by telephone or internet or in person at the Sterling special meeting, it will have no effect on such proposal.

The Merger Will Be Tax-Free to Holders of Sterling Common Stock as to the Shares of Umpqua Common Stock They Receive (page 137)

        The merger is intended to qualify as a "reorganization" within the meaning of Section 368(a) of the Code and it is a condition to the respective obligations of Sterling and Umpqua to complete the merger that each of Sterling and Umpqua receives a legal opinion to that effect. Accordingly, a Sterling common shareholder generally will recognize gain, but not loss, in an amount equal to the lesser of (1) the amount of gain realized (i.e., the excess of the sum of the amount of cash and the fair market value of the Umpqua common stock received pursuant to the merger over that holder's adjusted tax basis in its shares of Sterling common stock surrendered) and (2) the amount of cash received pursuant to the merger. Further, a Sterling common shareholder generally will recognize gain or loss with respect to cash received instead of fractional shares of Umpqua common stock that the Sterling common shareholder would otherwise be entitled to receive.

        For further information, see "United States Federal Income Tax Consequences of the Merger."

The U.S. federal income tax consequences described above may not apply to all holders of Sterling common stock. Your tax consequences will depend on your individual situation. Accordingly, we strongly urge you to consult your independent tax advisor for a full understanding of the particular tax consequences of the merger to you.

Interests of Sterling's Directors and Executive Officers in the Merger (page 101)

        Sterling shareholders should be aware that some of Sterling's directors and executive officers have interests in the merger and have arrangements that are different from, or in addition to, those of Sterling shareholders generally. Sterling's board of directors was aware of these interests and considered these interests, among other matters, when making its decision to adopt the merger agreement, and in recommending that Sterling shareholders vote in favor of approving the merger agreement.

        These interests include the following:

•

Pursuant to the merger agreement, each option to purchase shares of Sterling common stock outstanding immediately prior to the effective time (except for certain options with an exercise price significantly in excess of the value of the merger consideration, which Sterling will use commercially reasonable efforts to cancel prior to the effective time) will be converted into an option to purchase Umpqua common stock and each restricted stock unit in respect of Sterling common stock will be converted into a restricted stock unit in respect of Umpqua common stock (in each case, taking into account that, except for new equity award compensation granted prior to the effective time of the merger, the consummation of the merger and its related transactions will constitute the first trigger under equity awards that provide for "double trigger" acceleration of vesting).



•

Umpqua has entered into an employment agreement with J. Gregory Seibly, to be effective as of and subject to the occurrence of the effective time of the merger. Under the employment agreement, Mr. Seibly will receive an annual base salary of $565,000 and be eligible for an annual target bonus of 85% of his annual base salary. In settlement of Mr. Seibly's benefits under the Sterling Financial Corporation Change in Control Plan (the "Sterling Change in Control Plan"), Mr. Seibly will be entitled to a cash payment within 10 days following the

effective date of the merger of $2,129,439. In addition, upon the effective date of the merger, Mr. Seibly will receive a retention award of restricted Umpqua common stock with a grant date value of $1,419,626, which will vest, subject to Mr. Seibly's continued employment, upon the second anniversary of the effective date of the merger or upon any earlier termination of employment due to death, disability, termination without cause or termination for good reason (as such terms are defined in the employment agreement). Mr. Seibly is also eligible for a retention bonus of $452,000 if he remains employed through the second anniversary of the effective date of the merger. The payments in settlement of benefits under the Sterling Change in Control Plan, the retention award and the stay bonus payable to Mr. Seibly have an aggregate value of $4,001,065. Mr. Seibly will be eligible to participate in Umpqua's employee benefit plans on the same basis as similarly situated employees of Umpqua. The employment agreement has a term of two years.

•

Umpqua has entered into employment agreements with four additional executive officers of Sterling, to be effective as of and subject to the occurrence of the effective time of the merger. Under the employment agreements, David S. DePillo and Ezra A. Eckhardt will receive an annual base salary of $400,000 and be eligible for an annual target bonus of 60% of their annual base salary and Steven D. Hauschild and Andrew J. Schultheis will receive an annual base salary of $275,000 and be eligible for an annual target bonus of 50% of their annual base salary. In settlement of the executive officers' benefits under the Sterling Change in Control Plan, they will be entitled to a cash payment within 10 days following the effective date of the merger in the following amounts: Mr. DePillo $822,036; Mr. Eckhardt $1,336,505; Mr. Hauschild $530,345; and Mr. Schultheis $579,305. In addition, upon the effective date of the merger, each executive officer will receive a retention award of restricted Umpqua common stock with a grant date value in the following amounts: Mr. DePillo $548,024; Mr. Eckhardt $891,003; Mr. Hauschild $353,564; and Mr. Schultheis $386,203. The retention award will vest, subject to the executive officer's continued employment, upon the second anniversary of the effective date of the merger or upon any earlier termination of employment due to death, disability, termination without cause or termination for good reason (as such terms are defined in the employment agreement). Mr. Eckhardt is also eligible for a retention bonus of $320,000 if he remains employed through the second anniversary of the effective date of the merger. Each executive officer will be eligible to participate in Umpqua's employee benefit plans on the same basis as similarly situated employees of Umpqua. The employment agreements have a term of two years.



•

The payments in settlement of benefits under the Sterling Change in Control Plan, the retention awards and, solely in the case of Mr. Eckhardt, the stay bonus, payable to Messrs. DePillo, Eckhardt, Hauschild and Schultheis pursuant to the new employment agreements with Umpqua (as described above) have an aggregate value of $5,766,985.



•

Pursuant to the new employment agreements for Messrs. Seibly, DePillo, Eckhardt, Hauschild and Schultheis described above, if the executive officer's employment were terminated without cause or for good reason during the term of the employment agreement, subject to the execution of a release of claims, in addition to accelerated vesting of the retention award, he would be entitled to severance benefits in the form of continued base salary for a period equal to the greater of (1) nine months base salary and (2) two weeks base salary per year of service with Umpqua. See the "Quantification of Potential Payments to Sterling's Named Executive Officers in Connection with the Merger" beginning on page 106 for a quantification of the golden parachute compensation payable to each of Sterling's named executive officers.



•

Two Sterling executive officers, Patrick J. Rusnak and Robert G. Butterfield, are eligible for certain benefits under the Sterling Change in Control Plan. The plan provides for benefits if the executive officer's employment is involuntarily terminated by Sterling or if the executive officer is constructively discharged within 24 months following a transaction such as the merger.

Benefits under the plan are calculated based on (1) a multiple (24 months in the case of Mr. Rusnak and 18 months in the case of Mr. Butterfield) of monthly base compensation and target bonus, (2) the cost for a specified period (18 months for Mr. Rusnak and 18 months for Mr. Butterfield) of COBRA continuation coverage minus the then current employee portion of premiums for the same benefit, (3) a bonus payment for the year of termination prorated through the date of termination of employment and (4) outplacement services.

•

Under an existing letter agreement with Sterling, Leslie S. Biller, the Chairman of Sterling's board of directors, is entitled to a cash payment and accelerated vesting of certain stock options (which, if unexercised, will be converted into options to purchase Umpqua common stock) if he does not serve on the Umpqua board of directors following the merger. If the merger were consummated on March 31, 2014 and Mr. Biller does not serve on the Umpqua board of directors following that date, the cash payment would equal $375,000 and the intrinsic value of the accelerated stock options would equal $515,516 (based on a price per share of Sterling common stock of $28.78, the average closing price of Sterling common stock on the five days following the announcement of the merger).



•

If members of Sterling's board of directors do not serve on Umpqua's board of directors following the merger, the vesting of restricted stock units and stock options held by such directors will accelerate. If none of the members of Sterling's board of directors serve on Umpqua's board of directors, the aggregate value of restricted stock units and the intrinsic value of stock options subject to accelerated vesting would equal $1,669,030 (based on a price per share of Sterling common stock of $28.78, the average closing price of Sterling common stock on the five days following the announcement of the merger).



•

The members of Sterling's board of directors who will serve on Umpqua's board of directors have not yet been determined by Sterling's board of directors. Such members will be selected from a list that was mutually agreed upon by Umpqua and Sterling prior to the entry into the merger agreement. Each of these directors will receive the compensation provided to Umpqua directors from time to time. Umpqua directors currently receive a quarterly retainer of $12,500 (which amount may be higher for a director who serves as the chair of the board or a committee), an annual grant of restricted stock awards with a value of approximately $15,000 (which vest on the first anniversary of the grant date, subject to continued service through such date) and participation fees of $1,000 for each committee meeting attended. At least 70% of director compensation, excluding the restricted stock awards, is payable in Umpqua stock.



•

Prior to the effective time of the merger, the compensation and governance committee of Sterling's board of directors may grant (1) up to $5.7 million of equity award compensation in the ordinary course of business, consistent with past practice, and (2) up to $2 million of equity award compensation on terms and conditions determined by Sterling's compensation and governance committee. A substantial portion of the $2 million equity pool may be granted to Sterling's named executive officers who will continue employment with Umpqua following the merger, with the balance granted to other key Sterling executives who will continue employment with Umpqua following the merger. It is expected that grants with respect to both the $5.7 million and the $2 million equity pools will be made by the Sterling compensation and governance committee prior to the consummation of the merger. The merger shall not be considered a change in control under the terms of new equity awards granted prior to the effective time of the merger.

        For a more complete description of these interests, see "The Merger—Interests of Sterling's Directors and Executive Officers in the Merger."

Sterling Shareholders Who Do Not Vote in Favor of the Merger Agreement May Be Entitled To Assert Dissenters' Rights (page 110)

        Sterling shareholders who do not vote in favor of the approval of the merger agreement (including by failing to vote or marking "ABSTAIN" on their proxy card) and follow certain procedural steps will be entitled to dissenters' rights under chapter 23B.13 of the WBCA, provided they take the steps required to perfect their rights under 23B.13 of the WBCA. These procedural steps include, among others: (1) delivering to Sterling, before the vote on the merger at the Sterling special meeting, a notice of intent to demand payment for the shares of Sterling common stock if the merger is effected and (2) timely filing a payment demand after the merger is effected. For more information, see "The Merger—Dissenters' Rights in the Merger."

Conditions that Must Be Satisfied or Waived for the Merger To Occur (page 130)

        Currently, Sterling and Umpqua expect to complete the merger in the first half of 2014. As more fully described in this joint proxy statement/prospectus and in the merger agreement, the completion of the merger depends on a number of conditions being satisfied or, where legally permissible, waived. These conditions include (1) approval of the Sterling merger proposal by Sterling's shareholders and approval of the Umpqua merger proposal and the articles amendment proposal by Umpqua's shareholders, (2) authorization for listing on the NASDAQ Global Select Market of the shares of Umpqua common stock to be issued in the merger, (3) the receipt of required regulatory approvals, (4) effectiveness of the registration statement of which this joint proxy statement/prospectus is a part, (5) the absence of any order, injunction or other legal restraint preventing the completion of the merger or making the completion of the merger illegal, (6) subject to the materiality standards provided in the merger agreement, the accuracy of the representations and warranties of Umpqua and Sterling, (7) performance in all material respects by each of Umpqua and Sterling of its obligations under the merger agreement and (8) receipt by each of Umpqua and Sterling of an opinion from its counsel as to certain tax matters.

        Neither Sterling nor Umpqua can be certain when, or if, the conditions to the merger will be satisfied or waived, or that the merger will be completed.

Non-Solicitation (page 129)

        As more fully described in this joint proxy statement/prospectus and in the merger agreement, and subject to the exceptions summarized below, each of Sterling and Umpqua has agreed not to (1) solicit, initiate, knowingly encourage or knowingly facilitate, or take any other action designed to facilitate, any inquiries or proposals regarding an acquisition proposal, (2) participate in any discussions or negotiations regarding an alternative transaction or acquisition proposal or (3) enter into any agreement regarding any alternative transaction or acquisition proposal.

        However, each of Sterling or Umpqua, before shareholder approval of the merger agreement and, in the case of Umpqua, before shareholder approval of the articles amendment, is permitted to, following receipt of an acquisition proposal that is unsolicited and that the applicable board of directors determines is, or could reasonably be expected to result in, a superior proposal, (1) furnish information with respect to it and its subsidiaries to the party making the acquisition proposal and its representatives and financing sources under the terms of a confidentiality agreement no less restrictive than the one between the parties, and (2) participate in discussions and negotiations regarding the acquisition proposal.

        Each of Sterling and Umpqua is permitted to take the actions described above only if its board of directors determines in good faith, after receiving the advice of outside counsel, that the failure to take such action would be inconsistent with its fiduciary duties under applicable law.

        In addition, each of Sterling and Umpqua has agreed not to release any third party from, and to enforce, the confidentiality and standstill provisions of any agreement that it is party to as of the date of the merger agreement.

Termination of the Merger Agreement (page 131)

        The merger agreement can be terminated at any time prior to completion of the merger in the following circumstances:

•

by mutual consent of Umpqua and Sterling, if authorized by the board of directors of each;



•

by either Umpqua or Sterling if any governmental entity that must grant a requisite regulatory approval has (1) denied approval of any of the material transactions contemplated by the merger agreement and such denial has become final and nonappealable or any governmental entity of competent jurisdiction has issued a final nonappealable order permanently enjoining or otherwise prohibiting or making illegal the consummation of any of the material transactions contemplated by the merger agreement or (2) granted the requisite regulatory approval but such approval contains or results in the imposition of a materially burdensome regulatory condition (as later defined) with no meaningful possibility that such condition will be revised before the first anniversary of the date of the merger agreement (which we refer to as the "termination date"), unless the failure to obtain a requisite regulatory approval or to obtain such approval without a materially burdensome regulatory condition is due to the failure of the party seeking to terminate the merger agreement to perform or observe its covenants and agreements under the merger agreement;



•

by either Umpqua or Sterling if the merger has not been completed on or before the termination date, unless the failure of the merger to be completed by such date is due to the failure of the party seeking to terminate the merger agreement to perform or observe its covenants and agreements under the merger agreement;



•

by either Umpqua or Sterling if there is a breach of any of the covenants or agreements or any of the representations or warranties set forth in the merger agreement on the part of the other party which either individually or in the aggregate would constitute the failure of a closing condition of the terminating party and which is either not reasonably capable of being cured or not cured within the earlier of the termination date or the date 30 days following written notice to the party committing such breach (in each case, provided that the terminating party is not then in breach of any representation, warranty, covenant or other agreement contained in the merger agreement in a manner that would constitute the failure of a closing condition);



•

by either Umpqua or Sterling if (1) the Umpqua special meeting has concluded without the approval of the Umpqua merger proposal and the articles amendment proposal or (2) the Sterling special meeting has concluded without the approval of the Sterling merger proposal (in each case, provided that the terminating party has complied with its obligations with respect to holding its special meeting and recommendation of the merger);



•

by Sterling, before approval of the Umpqua merger proposal and the articles amendment proposal, if the board of directors of Umpqua (1) fails to recommend that Umpqua shareholders approve the Umpqua merger proposal and the articles amendment proposal, fails to include such recommendation in this joint proxy statement/prospectus, withdraws or modifies such recommendation in a manner adverse to Sterling or, in the case of a tender or exchange offer, fails to recommend rejection of such offer within 10 business days after the commencement of the offer, or (2) materially breaches certain obligations, including with respect to the non-solicitation of acquisition proposals or the calling a meeting of its shareholders and recommending that they approve the merger agreement; or

•

by Umpqua, before approval of the Sterling merger proposal, if the board of directors of Sterling (1) fails to recommend that Sterling shareholders approve the Sterling merger proposal, fails to include such recommendation in this joint proxy statement/prospectus, withdraws or modifies such recommendation in a manner adverse to Umpqua or, in the case of a tender or exchange offer, fails to recommend rejection of such offer within 10 business days after the commencement of the offer, or (2) materially breaches certain obligations, including with respect to the non-solicitation of acquisition proposals or the calling a meeting of its shareholders and recommending that they approve the merger agreement.

Termination Fee (page 132)

        If the merger agreement is terminated under certain circumstances involving alternative acquisition proposals, including circumstances involving changes in the recommendation of Sterling's or Umpqua's respective boards of directors, Sterling or Umpqua may be required to pay to the other party a termination fee equal to $75 million. These termination fees could discourage other companies from seeking to acquire or merge with Sterling or Umpqua.

Amendment to Umpqua's Articles of Incorporation (page 108 and Annex F)

        In connection with the merger, Umpqua's restated articles of incorporation will be amended at the effective time of the merger to increase the number of authorized shares of no par value common stock from 200,000,000 to 400,000,000 (which we refer to as the "articles amendment"), which is necessary for Umpqua to have enough authorized shares to issue the stock portion of the merger consideration. In addition to being necessary for Umpqua to issue the stock portion of the merger consideration, Umpqua's board of directors chose to propose an increase of 200,000,000 (in excess of the number required to authorize all of the shares to be issued in the merger) authorized shares to maintain Umpqua's flexibility in responding to future business and financing needs and opportunities.

Regulatory Approvals Required for the Merger (page 114)

        Subject to the terms of the merger agreement, both Sterling and Umpqua have agreed to use their reasonable best efforts to obtain all regulatory approvals necessary or advisable to complete the transactions contemplated by the merger agreement. These approvals include approvals from, among others, the Board of Governors of the Federal Reserve System (which we refer to as the "Federal Reserve Board"), the Federal Deposit Insurance Corporation (which we refer to as the "FDIC") and the Director of the Oregon Department of Consumer and Business Services (which we refer to as the "Oregon Director"). A notification to the Washington Department of Financial Institutions (which we refer to as the "Washington DFI") is also required. Umpqua and Sterling have filed applications and notifications to obtain the required regulatory approvals.

        Although neither Sterling nor Umpqua knows of any reason why these regulatory approvals cannot be obtained in a timely manner, Sterling and Umpqua cannot be certain when or if they will be obtained.

The Rights of Sterling Shareholders Will Change as a Result of the Merger (page 141)

        The rights of Sterling shareholders will change as a result of the merger due to differences in Umpqua's and Sterling's governing documents and states of incorporation. The rights of Sterling shareholders are governed by Washington law and by Sterling's articles of incorporation and bylaws, each as amended to date. Upon the completion of the merger, Sterling shareholders will become shareholders of Umpqua, as the continuing legal entity in the merger, and the rights of Sterling shareholders will therefore be governed by Oregon law and Umpqua's articles of incorporation and bylaws.

        For example, members of Umpqua's board of directors are elected by a plurality of votes cast, whereas members of Sterling's board of directors are elected if the votes cast for a nominee exceeds the votes cast against (other than in contested elections). For Umpqua's shareholders, the Oregon Control Share Act restricts a shareholder's ability to vote shares acquired in certain transactions not approved by the Umpqua board of directors, and no such rule exists under Washington law for Sterling. Finally, under Washington law, dissenters' rights are available to holders of shares of public companies, such as Sterling, whereas generally under Oregon law dissenters' rights are not available to holders of shares of public companies, such as Umpqua.

        See "Comparison of Shareholders' Rights" for a description of the material differences in shareholders' rights under each of the Umpqua and Sterling governing documents.

Information About the Companies (pages 61 and 62)

Umpqua Holdings Corporation

        Umpqua Holdings Corporation, an Oregon corporation, is a bank holding company with two principal operating subsidiaries, Umpqua Bank and Umpqua Investments, Inc. With headquarters in Roseburg, Oregon, Umpqua Bank provides a wide range of banking, wealth management, mortgage and other financial services to corporate, institutional and individual customers. Umpqua Investments is a registered broker-dealer and investment advisor with offices in Portland, Lake Oswego, and Medford, Oregon and products and services offered through Umpqua Bank stores. Umpqua Investments offers a full range of investment products and services including stocks, fixed income securities, mutual funds, annuities, options, retirement planning, money management services and life insurance. At September 30, 2013, Umpqua had, on a consolidated basis, assets of $11.6 billion, deposits of $9.1 billion and shareholders' equity of $1.7 billion.

        Umpqua's stock is traded on the NASDAQ Global Select Market under the symbol "UMPQ."

        The principal executive offices of Umpqua are located at One SW Columbia Street, Suite 1200, Portland, Oregon 97258, and its telephone number at that location is (503) 727-4100. Additional information about Umpqua and its subsidiaries is included in documents incorporated by reference in this joint proxy statement/prospectus. See "Where You Can Find More Information," beginning on page 161.

Sterling Financial Corporation

        Sterling Financial Corporation, with headquarters in Spokane, Washington, is organized under the laws of Washington State as the bank holding company for Sterling Savings Bank. Sterling Savings Bank is a Washington state-chartered commercial bank that does business as Sterling Bank in Washington, Oregon and Idaho and as Argent Bank in California. Sterling Savings Bank offers retail and commercial banking products and services, mortgage lending and wealth management to individuals, small businesses, commercial organizations and corporations. At September 30, 2013, Sterling had, on a consolidated basis, assets of $10.0 billion, deposits of $6.9 billion and shareholders' equity of $1.2 billion.

        Sterling's stock is traded on the NASDAQ Capital Market under the symbol "STSA."

        The principal executive offices of Sterling are located at 111 North Wall Street, Spokane, Washington 99201, and its telephone number at that location is (509) 358-8097. Additional information about Sterling and its subsidiaries is included in documents incorporated by reference in this joint proxy statement/prospectus. See "Where You Can Find More Information," beginning on page 161.

Litigation Relating to the Merger (page 116)

        Sterling, its directors and Umpqua are named as defendants in three lawsuits pending in the Superior Court of Washington in and for Spokane County, which have been consolidated under the caption In re Sterling Financial Corporation Merger Litigation, Lead No. 13-2-03848-4. The consolidated litigation generally seeks, among other things, an injunction against consummation of the merger, rescission of the merger if it is effected, damages in an unspecified amount, and the payment of plaintiffs' attorneys fees and costs. The defendants believe that the lawsuits are without merit. On January 16, 2014 the parties to the consolidated litigation entered into a memorandum of understanding to settle the consolidated litigation (such memorandum including plaintiffs' agreement to stay the consolidated litigation, except for proceedings relating to the settlement), subject to court approval and other customary conditions, including the execution of definitive documentation. Sterling shareholders who are members of the proposed settlement class will, at a later date, receive written notice containing the terms of the proposed settlement and proposed release of class claims and related matters. See "The Merger—Litigation Relating to the Merger" beginning on page 116.

Risk Factors (page 43)

        You should consider all the information contained in or incorporated by reference into this joint proxy statement/prospectus in deciding how to vote for the proposals presented in the joint proxy statement/prospectus. In particular, you should consider the factors described under "Risk Factors."

SELECTED CONSOLIDATED HISTORICAL FINANCIAL DATA OF UMPQUA

        The following selected consolidated financial information for the fiscal years ended December 31, 2008 through December 31, 2012 is derived from audited consolidated financial statements of Umpqua. The consolidated financial information as of and for the nine months ended September 30, 2013 and 2012 is derived from unaudited consolidated financial statements and, in the opinion of Umpqua's management, reflects all adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of these data for those dates. The results of operations for the nine months ended September 30, 2013 are not necessarily indicative of the results that may be expected for the entire fiscal year ending December 31, 2013. You should not assume the results of operations for any past periods indicate results for any future period. You should read this information in conjunction with Umpqua's consolidated financial statements and related notes thereto included in Umpqua's Annual Report on Form 10-K for the fiscal year ended December 31, 2012, and in Umpqua's Quarterly Report on Form 10-Q for the nine months ended September 30, 2013, which are incorporated by reference into this joint proxy statement/prospectus. See "Where You Can Find More Information."

SELECTED CONSOLIDATED HISTORICAL FINANCIAL DATA OF STERLING

        The following selected consolidated financial information for the fiscal years ended December 31, 2008 through December 31, 2012 is derived from audited consolidated financial statements of Sterling. The consolidated financial information as of and for the nine months ended September 30, 2013 and 2012 are derived from unaudited consolidated financial statements and, in the opinion of Sterling's management, reflects all adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of these data for those dates. The results of operations for the nine months ended September 30, 2013 are not necessarily indicative of the results that may be expected for the entire year ending December 31, 2013. You should not assume the results of operations for any past periods indicate results for any future period. You should read this information in conjunction with Sterling's consolidated financial statements and related notes thereto included in Sterling's Annual Report on Form 10-K for the year ended December 31, 2012, and in Sterling's Quarterly Report on Form 10-Q for the nine months ended September 30, 2013, which are incorporated by reference into this joint proxy statement/prospectus. See "Where You Can Find More Information."