UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of Earliest Event Reported): December 3, 2012

First PacTrust Bancorp, Inc.

(Exact Name of Registrant as Specified in Its Charter)

Registrant’s Telephone Number, Including Area Code: (949) 236-5211

Not Applicable

Former Name or Former Address, if Changed Since Last Report

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the Registrant under any of the following provisions:

First PacTrust Bancorp, Inc. (the “Company”) announced today that it intends to offer and sell an additional amount of its 7.50% Senior Notes due April 15, 2020 (the “Additional Notes”). The Additional Notes are being offered as additional notes under the indenture pursuant to which First PacTrust previously issued $33,000,000 in aggregate principal amount of 7.50% Senior Notes due April 15, 2020. The Company expects to use the net proceeds from the offering for possible acquisitions, support of organic growth, investments in, or extensions of credit to, its subsidiaries, investments in securities and for general corporate purposes. A copy of the press release announcing the offering of the Additional Notes is attached hereto as Exhibit 99.1.

This Current Report on Form 8-K and the attached press release shall not constitute an offer to sell or the solicitation of an offer to buy the securities described herein, nor shall there be any offer or sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful. The Company is conducting the offering pursuant to an effective Registration Statement on Form S-3 (File No. 333-170622) under the Securities Act of 1933, as amended. The senior notes offering is being made solely by means of a separate prospectus supplement and accompanying prospectus. Prospective investors should read the prospectus, the registration statement, the preliminary prospectus supplement and other documents filed by the Company with the Securities and Exchange Commission (the “SEC”) in connection with the senior notes offering for more complete information about the Company and the offering. Investors may obtain these documents without charge by visiting the SEC website at www.sec.gov. Alternatively, copies of the preliminary prospectus supplement and the prospectus relating to the offering may be obtained from UBS Securities LLC at 677 Washington Boulevard, Stamford, Connecticut 06901 or Raymond James & Associates, Inc., 880 Carillon Parkway, St. Petersburg, Florida 33716.

See Exhibit Index.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

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