Objective: The purpose of this study is to examine the effectiveness of group play therapy with cognitive behavioral approach on reformation the social maladjustment of girl adolescents with intellectual disabilities. Methods: The present study, is an Quasi-experimental study design with pre-test and post-test, and with experimental and control groups. population of this study, including all girl adolescents with intellectual disabilities (13-15 years), who attending in the special schools of  Hamadan city. Among this population, 16 students were diagnosed higher than average of Rutter test. These participants were matched in experimental and control groups (8 subjects each). The experimental group received eleven sessions of play therapy with cognitive and behavioral approach and control group were placed in the waiting list. Also experimental Group in the three months since the last session were continuously monitored. Research instrument were Rutter's behavior questionnaire and Sociometry. Results: Covariance analysis and t-test showed that play therapy with cognitive behavioral approach has caused to reduced social maladjustm-ent of adolescents in experimental group and increased their social interactions. Conclusion: The most important results of this study are effectiveness of group play therapy and usefulness of the cognitive - behavioral approach on reformation the social maladjustment. It can be argued that group play therapy with cognitive behavioral approach can reforms social maladjustment  girl adolescents with intellectual disabilities.