<PAGE>
 
                       SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.  20549

                                  FORM 10-K/A
                               (Amendment No. 1)

                 ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

   For the Fiscal Year Ended December 31, 1997    Commission File No. 0-3681

                          MERCURY GENERAL CORPORATION
             (Exact name of registrant as specified in its charter)


                        California                    95-221-1612
               (State or other jurisdiction        (I.R.S. Employer
               of incorporation or organization)   Identification No.)


     4484 Wilshire Boulevard, Los Angeles, California       90010
          (Address of principal executive offices)       (Zip Code)

       Registrant's telephone number, including area code:  (213)937-1060

           Securities registered pursuant to Section 12(b) of the Act

           Title of Class        Name of Exchange on Which Registered
           --------------        ------------------------------------
           Common Stock                New York Stock Exchange

           Securities registered pursuant to Section 12(g) of the Act

                                      NONE

Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the Registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.    Yes   X     No ____
                                          -----          

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405
of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K.  [_]

The aggregate market value of the Registrant's voting stock held by non-
affiliates of the Registrant at March 16, 1998, was approximately $1,636,718,299
(based upon the closing sales price of such date, as reported by the Wall Street
Journal).

At March 16, 1998,  the Registrant had issued and outstanding an aggregate of
55,219,513 shares of its Common Stock.

                      Documents Incorporated by Reference

Proxy statement for the Annual Meeting of Stockholders of Registrant to be held
on May 13, 1998 (only portions of which are incorporated by reference).
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Mercury General Corporation is adding Exhibit 27 Financial Data Schedules to its
annual report on Form 10-K for the fiscal year ended December 31, 1997, pursuant
to the requirements of Item 601(c)(2)(iii) of Regulation S-K.


                                    PART IV

ITEM 14.  EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS ON FORM 8-K
          ---------------------------------------------------------------

     (a) The following documents are filed as a part of this report:

     3. Exhibits:
 
          27.1    Restated Financial Data Schedule For
                  9 Months Ending 9/30/97
              
          27.2    Restated Financial Data Schedule For
                  6 Months Ending 6/30/97
              
          27.3    Restated Financial Data Schedule For
                  3 Months Ending 3/31/97
              
          27.4    Restated Financial Data Schedule For
                  Year Ending 12/31/96
              
          27.5    Restated Financial Data Schedule For
                  9 Months Ending 9/30/96
              
          27.6    Restated Financial Data Schedule For
                  6 Months Ending 6/30/96
              
          27.7    Restated Financial Data Schedule For
                  3 Months Ending 3/31/96
              
          27.8    Restated Financial Data Schedule For
                  Year Ending 12/31/95

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                                  SIGNATURES

     Pursuant to the requirements of Section 13 or 15(d) 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.

                                         MERCURY GENERAL CORPORATION



                                         BY: /s/ George Joseph
                                             -----------------------
                                                George Joseph
                                         Chief Executive Officer and
                                         Chairman of the Board

June 17, 1998

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