There are about 1.5 to 3 million exceptional children in Iran. By this great population, educational system of Iran must undoubtedly pay special attention to these children. One of the most distinct characteristics of these people is their inability to establish effective communication with the society. Current research was conducted to investigate the efficacy of educational games on the ability of social skills in mentally retarded girls aging 8-12 years. This study was semi-experimental study with pre-test and post-test. The sample group contained 20 mentally retarded girls according to the research criteria, by which whole of them were selected because of a small number of cases. 10 of them were randomly assigned to the test group, while the other 10 were assigned to the control group. The test group was trained with the social skills using directed educational games, while the control group followed the normal trend of the class. Wailand's social growth test was applied to both groups. In this study, ANCOVA was used for analysis. Results suggest that the test group had significantly higher scores as compared to the control group. This finding is in agreement with those of other researchers and indicates capabilities of the educational games in improving the ability of social skills.