<PAGE>
 
                                                                      EXHIBIT 11


                ICF KAISER INTERNATIONAL, INC. AND SUBSIDIARIES
          COMPUTATION OF PRIMARY AND FULLY DILUTED EARNINGS PER SHARE
 
<TABLE>
<CAPTION>

 
                                                             Nine Months Ended September 30,
                                                             ------------------------------- 
                                                                 1997               1996
                                                             -------------       -----------  
                                                                       (Unaudited)
<S>                                                          <C>                 <C>
Primary:
 
     Net income available for common shareholders              $   170,000       $ 2,089,000
                                                               ===========       ===========  
     Weighted average of common shares                                       
      outstanding not included in                                             
      amounts below                                             22,381,538        21,954,783
                                                                              
     Weighted average of common shares                                        
      issuable on exercise of outstanding                                     
      stock options and warrants                                    49,698                 -
                                                               -----------       -----------  
     Weighted average of common and                                           
      common equivalent shares                                                
      outstanding, as adjusted                                  22,431,236        21,954,783
                                                                     or               or
                                                                22,431,000        21,955,000
                                                               ===========       ===========  
     Net income per common share                               $      0.01       $      0.10
                                                               ===========       =========== 

Fully Diluted:                                                                
                                                                              
     Net income available for common shareholders              $   170,000       $ 2,089,000     
                                                               ===========       =========== 
                                                                              
     Weighted average of common shares                                        
      outstanding as adjusted for primary                                     
      computation                                               22,431,236        21,954,783
                                                                              
     Weighted average of additional common                                    
      shares issuable on exercise of                                          
      outstanding stock options and warrants                        79,523                 -
                                                               -----------       -----------  
     Weighted average of common and                                           
      common equivalent shares                                                
      outstanding, as adjusted                                  22,510,759        21,954,783
                                                                     or               or
                                                                22,511,000        21,955,000
                                                               ===========       =========== 
     Net income per common share                               $      0.01       $      0.10
                                                               ===========       =========== 
 
 </TABLE>
 
<PAGE>
 
                                                                      EXHIBIT 11

                ICF KAISER INTERNATIONAL, INC. AND SUBSIDIARIES
          COMPUTATION OF PRIMARY AND FULLY DILUTED EARNINGS PER SHARE
 
<TABLE> 
<CAPTION> 
 
                                                      Three Months Ended September 30,
                                                      --------------------------------
                                                           1997              1996
                                                      -------------     -------------- 
                                                                 (Unaudited)
<S>                                                     <C>             <C> 
Primary:
 
     Net income available for common shareholders       $   120,000       $   224,000
                                                        ===========       =========== 
     Weighted average of common shares                                
      outstanding not included in                                     
      amounts below                                      22,501,784        22,226,844
                                                                      
     Weighted average of common shares                                
      issuable on exercise of outstanding                             
      stock options and warrants                                  -                 -
                                                        -----------       ----------- 
     Weighted average of common and                                   
      common equivalent shares                                        
      outstanding, as adjusted                           22,501,784        22,226,844
                                                             or                or
                                                         22,502,000        22,227,000        
                                                        ===========       =========== 
     Net income per common share                        $      0.01       $      0.01
                                                        ===========       =========== 
Fully Diluted:                                                        
                                                                      
     Net income available for common shareholders       $   120,000       $   224,000
                                                        ===========       =========== 
     Weighted average of common shares                                
      outstanding as adjusted for primary                             
      computation                                        22,501,784        22,226,844
                                                                      
     Weighted average of additional common                            
      shares issuable on exercise of                                  
      outstanding stock options and warrants                 92,240                 -
                                                        -----------       ----------- 
     Weighted average of common and                                   
      common equivalent shares                                        
      outstanding, as adjusted                           22,594,024        22,226,844
                                                             or                or
                                                         22,594,000        22,227,000
                                                        ===========       ===========
     Net income per common share                        $      0.01       $      0.01
                                                        ===========       =========== 
</TABLE>