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): November 14, 2011

SUFFOLK BANCORP

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (631) 208-2400

N/A

(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 (see General Instruction A.2. below):

Item 3.01 Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing.

On November 18, 2011, Suffolk Bancorp (“Suffolk”) reported that on November 14, 2011, it received a letter from Nasdaq that Suffolk was not in compliance with Nasdaq Listing Rule 5250(c)(1) due to Suffolk’s delay in filing its Quarterly Report on Form 10-Q for the period ended September 30, 2011.

As previously announced on November 14, 2011, Suffolk has received a Delisting Determination letter from Nasdaq for failing to timely file its Quarterly Reports on Form 10-Q for the quarters ended March 31, 2011 and June 30, 2011 with the Securities and Exchange Commission in violation of Nasdaq Listing Rule 5250(c)(1). Nasdaq has notified Suffolk that the failure to file its Quarterly Report on Form 10-Q for the period ended September 30, 2011 is an additional basis for delisting Suffolk’s securities. Suffolk has appealed the delisting determination and a hearing before a Nasdaq Hearings Panel has been scheduled for January 19, 2012. Suffolk has also requested a stay of any delisting of Suffolk common stock until the hearing takes place and a decision is issued.

This filing includes statements about Suffolk which look to the future. These forward-looking statements are based upon current management expectations, and may, therefore, involve risks and uncertainties that cannot be predicted or quantified and are beyond Suffolk’s control and are subject to a variety of uncertainties that could cause future results to vary materially from Suffolk’s historical performance, or from current expectations. Factors affecting Suffolk Bancorp include particularly, but are not limited to: our failure to meet the deadlines set forth in our Plan of Compliance filed with Nasdaq on September 21, 2011 for filing our Quarterly Reports for the quarters ended March 31, 2011 and June 30, 2011; a refusal by Nasdaq to grant a stay of delisting until the conclusion of the Nasdaq hearing and issuance of a decision; a failure to comply with Nasdaq rules; results of regulatory examinations; any failure by us to comply with our written agreement with the OCC (the “Agreement”) or the individual minimum capital ratios for the Bank established by the OCC; the cost of compliance with the Agreement; failure by us to maintain effective internal controls over financial reporting; potential litigation or regulatory action relating to the matters resulting in our failure to file on time our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2011, June 30, 2011 and September 30, 2011 or resulting from the revisions to our earnings previously announced on April 12, 2011 or the restatement of our financial statements for the quarterly period ended September 30, 2010 and year ended December 31, 2010; and the potential that net charge-offs are higher than expected or for further increases in our provision for loan losses.

Item 9.01 Financial Statements and Exhibits.

SIGNATURE

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.

EXHIBIT INDEX