<PAGE>
 
                       SECURITIES AND EXCHANGE COMMISSION

                              WASHINGTON, DC 20549
                                        
                                FORM 10-K405/A

                  Annual report pursuant to Section 13 of the
                  Securities Exchange Act of 1934, as amended

                    For the fiscal year ended March 31, 1998

                          Commission File No.: 0-27404

                               PFF BANCORP, INC.
             (exact name of registrant as specified in its charter)

         DELAWARE                                         95-4561623
(State or other jurisdiction of                   (I.R.S. Employer I.D. No.)
 incorporation or organization)

               350 SOUTH GAREY AVENUE, POMONA, CALIFORNIA  91766
                    (Address of principal executive offices)

       Registrant's telephone number, including area code: (909) 623-2323
       Securities registered pursuant to Section 12(b) of the Act:  NONE
          Securities registered pursuant to Section 12(g) of the Act:

                    COMMON STOCK, PAR VALUE $0.01 PER SHARE
                                (Title of class)

                             NASDAQ NATIONAL MARKET
                     (Name of exchange on which registered)

     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 the registrant's knowledge, in definitive proxy or information
statements incorporated by reference in Part III of the Form 10-K or any
amendment to this Form 10-K. [X]

     The aggregate market value of the voting stock held by non-affiliates of
the registrant, i.e., persons other than the directors and executive officers of
the registrant, was $ 339,466,088, based upon the last sales price as quoted on
The NASDAQ National Market for June 23, 1998.

     The number of shares of Common Stock outstanding as of June 23, 1998:
17,103,690


                      DOCUMENTS INCORPORATED BY REFERENCE
                                        
     Portions of the Registrant's Proxy Statement to be filed with the
Securities and Exchange Commission in connection with the Annual Meeting of
Stockholders to be held September 16, 1998 are incorporated by reference in Part
III hereof.
<PAGE>
 
                                  SIGNATURES

     Pursuant to the requirements of Section 13 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.

                                        PFF BANCORP, INC.


                                        BY:/s/ LARRY M. RINEHART
                                           -------------------------------
                                           Larry M. Rinehart
DATED: June 23, 1998                       President, Chief Executive Officer
                                           and Director

     Pursuant to the requirements of the Securities and Exchange Act of 1934,
this report has been signed by the following persons in the capacities and on
the dates indicated.

<TABLE> 
<CAPTION> 
              NAME                                TITLE                         DATE
------------------------------------------------------------------------------------------
<S>                                   <C>                                    <C> 
/s/ LARRY M. RINEHART                                                                     
---------------------------------                                                         
Larry M. Rinehart                     President, Chief Executive             June 23, 1998
                                      Officer and Director                                
                                      (Principal Executive Officer)                       
                                                                                          
/s/ GREGORY C. TALBOTT                                                                    
---------------------------------                                                         
Gregory C. Talbott                    Executive Vice President, Chief        June 23, 1998
                                      Financial Officer and Treasurer                     
                                      (Principal Financial and                            
                                      Accounting Officer)                                 
                                                                                          
/s/ ROBERT W. BURWELL                                                                     
---------------------------------                                                         
Robert W. Burwell                     Director                               June 23, 1998
                                                                                          
                                                                                          
/s/ WILLIAM T. DINGLE                                                                     
---------------------------------                                                         
William T. Dingle                     Director                               June 23, 1998
                                                                                          
                                                                                          
/s/ CURTIS W. MORRIS                                                                      
---------------------------------                                                         
Curtis W. Morris                      Director                               June 23, 1998
                                                                                          
                                                                                          
/s/ ROBERT D. NICHOLS                                                                     
---------------------------------                                                         
Robert D. Nichols                     Director                               June 23, 1998
                                                                                          
                                                                                          
/s/ JIL H. STARK                                                                          
---------------------------------                                                         
Jil H. Stark                          Director                               June 23, 1998
</TABLE> 
                                                                             
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