Introduction: Prosocial behaviors expand participation in society; therefore, these behaviors provide objective conditions for increasing social friendship and reducing the social exclusion. Thus, promoting these behaviors leads to increasing social capital in the community. The purpose of this study was to see the effectiveness of cognitive behavioral group therapy to improve prosocial behavior of high school female students in city of Yazd. 
Methods: The semi experimental design with pre-test/post-test with control group was used. Then 26 subjects were randomly assigned to two equal-sized experimental and control groups. The data was collected through Prosocial Tendencies Measure Revised 2002. The experimental group participated in eight sessions of cognitive behavioral group therapy for improving prosocial behavior. Data was analyzed by analysis of covariance. 
Results: The results showed that there was significant difference between mean scores of experimental and control groups at post-test. It is concluded that cognitive behavioral group therapy can increase the prosocial behaviors among high school female students.
Conclusions: The cognitive behavioral group therapy, raises the prosocial behaviors significantly, therefore it can be considered to desirable model for improving these behaviors.