Sexual relation is a very important part of the marital relationship. Any problem in the marital relationship affects the family and society cohesion. This study aim to determine the effect of Group sexual assertiveness training on Sexual assertiveness of Female Students. This quasi-experimental pre and posttest study was conducted on 80 married female students of Sistan and Baluchestan University (southeast of Iran), from 1 July 2018 to 30 March 2019.Students were selected and randomly allocated in the two intervention and control groups. The intervention group received group sexual assertiveness training in the 4 two-hourly sessions over a period of two weeks. The control group did not receive any training. The data were collected before and 12 weeks after the intervention by Hurlbert’s sexual assertiveness questionnaire, and then were analyzed. After the implementation of group sexual assertiveness training, the mean score of sexual assertiveness significantly increased in the intervention group compared to the control group (p=0.01). It is recommended to add sexual assertive training to the pre-marriage education, especially in cultures in which women have a low level of sexual assertiveness