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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 11-K

ý ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2007 or

o
TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from                        to                         .

Commission File No. 00-11337

A.
FULL TITLE OF THE PLAN AND THE ADDRESS OF THE PLAN, IF DIFFERENT FROM THAT OF THE ISSUER NAMED BELOW:

Foothill Independent Bank
Partners in Your Future
401(k) Profit Sharing Plan
PacWest Bancorp
120 Wilshire Blvd.
Santa Monica, California 90401

B.
NAME OF THE ISSUER OF THE SECURITIES HELD PURSUANT TO THE PLAN AND THE ADDRESS OF ITS PRINCIPAL EXECUTIVE OFFICE:

PacWest Bancorp
401 West "A" Street
San Diego, California 92101


FOOTHILL INDEPENDENT BANK
PARTNERS IN YOUR FUTURE
401(k) PROFIT SHARING PLAN

Index

 
   Page

Reports of Independent Registered Public Accounting Firms
 
2

Statements of Net Assets Available for Benefits—December 31, 2007 (Liquidation Basis) and 2006 (Liquidation Basis)
 
4

Statement of Changes in Net Assets Available for Benefits—Year ended December 31, 2007 (Liquidation Basis)
 
5

Notes to Financial Statements
 
6

Supplemental Schedule
 
 

Schedule H, Line 4i—Schedule of Assets (Held at End of Year)—December 31, 2007 (Liquidation Basis)
 
10

All other schedules are omitted because they are not required or applicable pursuant to the Employee Retirement Income Security Act of 1974 (ERISA) and Department of Labor regulations.


Report of Independent Registered Public Accounting Firm

The 401K Committee
Foothill Independent Bank Partners in Your Future 401(k) Profit Sharing Plan

        We have audited the accompanying statement of net assets available for benefits of Foothill Independent Bank Partners in Your Future 401(k) Profit Sharing Plan (the Plan) as of December 31, 2007 (liquidation basis) and the related statement of changes in net assets available for benefits for the year ended December 31, 2007 (liquidation basis). These financial statements are the responsibility of the Plan's management. Our responsibility is to express an opinion on these financial statements based on our audit. The financial statement of the Plan as of December 31, 2006 (liquidation basis) was audited by other auditors, whose report dated August 27, 2007, expressed an unqualified opinion on that financial statement.

        We conducted our audit in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audit provides a reasonable basis for our opinion.

        In our opinion, the financial statements referred to above present fairly, in all material respects, the net assets available for benefits of the Plan as of December 31, 2007 (liquidation basis), and the changes in net assets available for benefits for the year ended December 31, 2007 (liquidation basis) in conformity with U.S. generally accepted accounting principles.

        As discussed in Note 1(b) to the accompanying financial statements, on May 9, 2006, Foothill Independent Bancorp, parent of Foothill Independent Bank ("Bank") approved an Agreement and Plan of Merger with PacWest Bancorp, formerly known as First Community Bancorp, which provided for the acquisition of Foothill Independent Bank. An application for termination was filed with the Internal Revenue Services on January 16, 2007. A favorable determination letter was received on July 20, 2007. Subsequent to September 4, 2007, PacWest Bancorp began the distribution process. Participant balances are to be distributed to participant IRA accounts or the participants current employer's Plan.

        Our audit was performed for the purpose of forming an opinion on the 2007 financial statements taken as a whole. The supplemental schedule, Schedule H, Line 4i—Schedule of Assets (Held at End of Year) as of December 31, 2007 liquidation basis is presented for purpose of additional analysis and is not a required part of the basic financial statements, but is supplementary information required by the Department of Labor's Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. This supplemental schedule is the responsibility of the Plan's management. The supplemental schedule has been subjected to the auditing procedures applied in the audit of the basic 2007 financial statements and, in our opinion, is fairly stated, in all material respects, in relation to the basic 2007 financial statements taken as a whole.

/s/ Squar, Milner, Peterson, Miranda & Williamson, LLP

Newport Beach, California
June 27, 2008

See accompanying notes to financial statements.

2


Report of Independent Registered Public Accounting Firm

To the Participants and the Administrator of the
Foothill Independent Bank Partners in Your Future 401(k) Profit Sharing Plan:

        We have audited the accompanying statement of net assets available for benefits of the Foothill Independent Bank 401(k) Partners in Your Future Profit Sharing Plan (the Plan) as of December 31, 2006. This financial statement is the responsibility of the Plan's management. Our responsibility is to express an opinion on this financial statement based on our audit.

        We conducted our audit in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audit provides a reasonable basis for our opinion.

        In our opinion, the financial statement referred to above presents fairly, in all material respects, the net assets available for benefits of the Plan as of December 31, 2006 in conformity with U.S. generally accepted accounting principles.

        As discussed in Note 1(b) to the Financial Statements, On May 2, 2006, the Board of Directors of Foothill Independent Bancorp, the Plans sponsor, voted to terminate the Plan. In accordance with accounting principles generally accepted in the United States of America, the Plan has changed its basis of accounting from the ongoing Plan basis used in presenting the 2005 Financial Statements to the liquidation basis used in presenting the 2006 Financial Statements.

/s/ Grobstein, Horwath & Company LLP

Costa Mesa, California
August 27, 2007

See accompanying notes to financial statements.

3


FOOTHILL INDEPENDENT BANK
PARTNERS IN YOUR FUTURE
401(k) PROFIT SHARING PLAN

Statements of Net Assets Available for Benefits

December 31, 2007 (Liquidation Basis) and 2006 (Liquidation Basis)

 
   2007
   2006
Investments at fair value:            
  Mutual funds   $ 525,598   $ 2,761,676
  Common stock     1,247,826     7,425,006
  Common/collective trust     137,829     759,204
  Participant loans     —     97,233
   
 
    Total investments     1,911,253     11,043,119
   
 
    Net assets available for benefits   $ 1,911,253     11,043,119
   
 

See accompanying notes to financial statements.

4


FOOTHILL INDEPENDENT BANK
PARTNERS IN YOUR FUTURE
401(k) PROFIT SHARING PLAN

Statement of Changes in Net Assets Available for Benefits

Year ended December 31, 2007 (Liquidation Basis)

Additions (deductions) to net assets attributable to:        
  Investment income:        
    Interest and dividends   $ 237,788  
    Net depreciation in fair value of investments     (218,824 )
   
 
      Total investment income     18,964  
   
 

Deductions from net assets attributable to:
 
 
 
 
  Benefits paid / distributions to participants     9,150,780  
  Administrative expenses     50  
   
 
      Total deductions     9,150,830  

Decrease in net assets
 
 
(9,131,866
)
   
 
Net assets available for benefits:        
  Beginning of the year     11,043,119  
   
 
  End of the year   $ 1,911,253  
   
 

See accompanying notes to financial statements.

5


FOOTHILL INDEPENDENT BANK
PARTNERS IN YOUR FUTURE
401(k) PROFIT SHARING PLAN

Notes to Financial Statements

December 31, 2007 (Liquidation Basis) and 2006 (Liquidation Basis)

(1) Description of the Plan

        The following description of the Foothill Independent Bank Partners in Your Future 401(k) Profit Sharing Plan (the Plan) provides only general information. Participants should refer to the Plan agreement for a complete description of the Plan's provisions.

        The Plan is a defined contribution plan which provides retirement benefits for eligible employees of Foothill Independent Bank and its subsidiaries (the Company) that have elected to participate in the Plan. Foothill Independent Bancorp and its subsidiary Foothill Independent Bank were acquired by PacWest Bancorp, formerly known as First Community Bancorp, on May 9, 2006, upon which all assets of the plan were frozen. As successor to Foothill Independent Bancorp, the Plan is administered by PacWest Bancorp. PacWest Bancorp is in the process of terminating the Plan and has received favorable determination from the Internal Revenue Service (the IRS). The Plan is subject to the provisions of the Employee Retirement Income Security Act of 1974 (ERISA).

        On May 2, 2006 the Board of Directors of Foothill Independent Bancorp, the Plans sponsor, voted to terminate the Plan. On May 9, 2006, the Board of Directors of Foothill Independent Bancorp approved an Agreement and Plan of Merger with PacWest Bancorp, which provided for the acquisition of Foothill Independent Bank. An application for termination was filed with the Internal Revenue Services on January 16, 2007. A favorable determination letter was received on July 20, 2007. Subsequent to September 4, 2007, PacWest Bancorp began the distribution process. Participant balances are to be distributed to participant IRA accounts or the participants current employer's Plan

        The Plan is no longer accepting participant contributions and no contributions were received in 2007. The plan last received contributions in 2006. While contributions were accepted, employees of the Company who completed six months of service were eligible to participate in the Plan. There was no age requirement. Participants could contribute, under a salary reduction agreement, up to 100% of their eligible compensation, as defined, but not to exceed the dollar amount allowed by law, which was $15,000 for 2006. Participants could also contribute amounts representing distributions (rollovers) from other tax favored plans, and participants age 50 and over may make unmatched "catch-up" contributions in accordance with Internal Revenue Code (IRC) regulations and limitations.

        Each participant account was credited with the participant's contributions, allocations of the Company's matching contribution and earnings or losses. Earnings of the various funds are allocated to the participant balances according to the ratio that a participant's account balance or shares held in a given fund bears to the total of all account balances or shares held in the fund.

6

FOOTHILL INDEPENDENT BANK
PARTNERS IN YOUR FUTURE
401(k) PROFIT SHARING PLAN

Notes to Financial Statements (Continued)

December 31, 2007 (Liquidation Basis) and 2006 (Liquidation Basis)

(1) Description of the Plan (Continued)

        Participant contributions were immediately fully vested. The Company fully vested the matching contributions effective with the acquisition of Foothill Independent Bancorp.

        A participant may have received a distribution of his or her entire vested account balance upon the participant's termination of employment. While employed, a participant may receive a distribution of his or her rollover account and employee contribution deferrals for reason of financial hardship, in accordance with Plan provisions. The Plan is currently in the process distributing the Plan assets to the participants.

        Loans to participants were made, at the discretion of the Plan's administrator, for up to 50% of the participants vested account balance in an amount not less than $1,000 and not to exceed $50,000. Such loans are collateralized by the participant's vested balance in the Plan and were for a fixed term requiring regular payments. The loans bear a reasonable rate of interest. Effective with the acquisition of Foothill Indpendent Bancorp all assets were frozen however routine loan payments were accepted by the Plan. Participants had the ability to pay the loan balance in full prior to termination of the plan or deem their outstanding loan balance as a distribution, which is subject to certain tax consequences. There were no loans outstanding at December 31, 2007.

(2) Significant Accounting Policies

        The financial statements of the Plan have been prepared on the liquidation basis of accounting as of December 31, 2007 and December 31, 2006 and for the years then ended.

        The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities in the statements of net assets available for benefits and the additions and deductions in the statements of changes in net assets available for benefits, as well as the disclosure of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates.

        The Plan's investments are maintained in publicly traded securities and are carried at fair value based on the published market quotations. The Plan's investments in participant loans are valued at

7

FOOTHILL INDEPENDENT BANK
PARTNERS IN YOUR FUTURE
401(k) PROFIT SHARING PLAN

Notes to Financial Statements (Continued)

December 31, 2007 (Liquidation Basis) and 2006 (Liquidation Basis)

(2) Significant Accounting Policies (Continued)

cost, which approximates fair value. All investment values are considered to approximate the liquidation basis of accounting.

        The Plan also had investments in PacWest Bancorp common stock in 2007 and 2006. These shares are valued at quoted market prices on a trade-date basis.

        Appreciation (depreciation) in fair value of investments is the realized gain (loss) on disposition of investments plus the unrealized increase (decrease) in fair value of investments held from the beginning of the plan year or date of purchase, whichever is later. Purchases and sales of investments are recorded on a trade-date basis. Interest income and dividends are recorded on the date received.

        Participant benefits are recorded when paid.

        Administrative expenses of the Plan are paid by the Company or the successor.

        The Plan provides for various investment options in money market funds, mutual funds, common stocks, corporate debt, and government securities. Investment securities are exposed to various risks such as interest rate, market, and credit. Due to the level of uncertainty related to changes in the value of investment securities, it is at least reasonably possible that changes in the various risk factors, in the near term, could materially affect participants' account balances and the amounts reported in the financial statements.

(3) Investments

        The following table presents the fair value of investments as of December 31, 2007 and 2006, with individual investments representing 5% or more of the Plan's net assets available for benefits separately identified:

Investment
   2007
   2006
  
PacWest Bancorp common stock     1,247,826     7,425,006  
Oakmark Equity and Income II     134,191     756,947  
Janus Adv:Forty/S     176,395     618,905  
Union Bank of California-Stable Fund     139,246     759,204  
PIMCO Real Return Bond A     96,998     287,477 *
Investments less than 5% of Plan assets     116,597     1,098,347  
Loan to participants     —     97,233  
   
 
 
  Total   $ 1,911,253   $ 11,043,119  
   
 
 
*
Less than 5% as of December 31, 2005, presented for comparison only.

8


FOOTHILL INDEPENDENT BANK
PARTNERS IN YOUR FUTURE
401(k) PROFIT SHARING PLAN

Schedule H, Line 4i—Schedule of Assets (Held at End of Year)

December 31, 2007 (Liquidation Basis)

(3) Investments (Continued)

        During the year ended December 31, 2007, the Plan's investments (including investment securities bought, sold and held during the year) appreciated (depreciated) as follows:

Investment
   2006
  
PacWest Bancorp common stock   $ (612,860 )
Mutual funds     394,036  
   
 
  Total   $ (218,824 )
   
 

(4) Party-in-interest Transactions

        The Plan's investment in the PacWest Bancorp's common stock amounted to $1,247,826 at December 31, 2007 and $7,425,006 at December 31, 2006. The Plan held 30,253 and 142,051 shares of the PacWest Bancorp common stock as of December 31, 2007 and 2006. Such investments represented 65% and 67% of the Plan's net assets available for benefits at December 31, 2007 and 2006.

(5) Tax Status

        The IRS has determined and informed the Company by letters dated April 29, 2002, that the Plan and related trust were designed in accordance with applicable requirements of the Internal Revenue Code. The Plan has been amended since receiving the IRS determination letter; however, the Company and the Plan administrator believe that the Plan is currently designed and operated in compliance with the applicable requirements of the Internal Revenue Code and the Plan and related trust continue to be tax- exempt. Therefore, no provision for income taxes has been included in the Plan's financial statements. The Plan received a favorable determination letter during the year ended December 31, 2007, (See Note 1(b), under Plan Termination).

9

FOOTHILL INDEPENDENT BANK
PARTNERS IN YOUR FUTURE
401(k) PROFIT SHARING PLAN

Schedule H, Line 4i—Schedule of Assets (Held at End of Year)

December 31, 2007 (Liquidation Basis)

(5) Tax Status (Continued)


FOOTHILL INDEPENDENT BANK
PARTNERS IN YOUR FUTURE
401(k) PROFIT SHARING PLAN

Schedule H, Line 4i-Schedule of Assets (Held at End of Year)

December 31, 2007 (Liquidation Basis)

(a)
Identity of issue, borrower,
lessor, or similar party
   (b)
Description of investment, including maturity date, rate of interest, collateral, par, or maturity value
   (c)
Number of shares
   (d)
Current value
  Union Bank of California, N.A.   Stable Value Fund A   139,246     139,246
  PIMCO   PIMCO Real Return Bond A   8,148     96,998
  Oakmark   Oakmark Equity and Income II   4,842     134,191
  MFS   MFS Value A   381     10,097
  Dreyfus   Dreyfus S&P 500   1,237     51,121
  Janus Group   Janus Adv Capital Appreciation S   4,135     176,395
  Franklin/Templeton   Franklin Flex Cap Growth A   264     12,804
  Wells Fargo Investment   Advantage Small Cap Value A   924     26,805
  Franklin/Templeton   Templeton Foreign A   710     8,888
  Ivy Science and Technology Fund   Ivy Science and Technology Y   218     6,882

Common stock:
 
 
 
 
 
 
 
  PacWest Bancorp   Common stock   30,258     1,247,826
           
        Total investments held at end of year       $ 1,911,253
           

10


SIGNATURES

        Pursuant to the requirements of the Securities Exchange Act of 1934, the trustees (or other persons who administer the employee benefit plan) have duly caused this annual report to be signed on its behalf by the undersigned hereunto duly authorized.

  Foothill Independent Bank
Partners in Your Future
401(k) Profit Sharing Plan

Date: June 30, 2007
/s/  JEFFREY T. KRUMPOCH      
Jeffrey T. Krumpoch
 Senior Vice President
PacWest Bancorp

11



QuickLinks

FOOTHILL INDEPENDENT BANK PARTNERS IN YOUR FUTURE 401(k) PROFIT SHARING PLAN Index
Report of Independent Registered Public Accounting Firm
Report of Independent Registered Public Accounting Firm
FOOTHILL INDEPENDENT BANK PARTNERS IN YOUR FUTURE 401(k) PROFIT SHARING PLAN Statements of Net Assets Available for Benefits December 31, 2007 (Liquidation Basis) and 2006 (Liquidation Basis)
FOOTHILL INDEPENDENT BANK PARTNERS IN YOUR FUTURE 401(k) PROFIT SHARING PLAN Statement of Changes in Net Assets Available for Benefits Year ended December 31, 2007 (Liquidation Basis)
FOOTHILL INDEPENDENT BANK PARTNERS IN YOUR FUTURE 401(k) PROFIT SHARING PLAN Notes to Financial Statements December 31, 2007 (Liquidation Basis) and 2006 (Liquidation Basis)
FOOTHILL INDEPENDENT BANK PARTNERS IN YOUR FUTURE 401(k) PROFIT SHARING PLAN Schedule H, Line 4i—Schedule of Assets (Held at End of Year) December 31, 2007 (Liquidation Basis)
FOOTHILL INDEPENDENT BANK PARTNERS IN YOUR FUTURE 401(k) PROFIT SHARING PLAN Schedule H, Line 4i-Schedule of Assets (Held at End of Year) December 31, 2007 (Liquidation Basis)
SIGNATURES