The current study aimed to investigate the effectiveness of a group counselling program based on acceptance and commitment therapy (ACT) in improving the body image of adolescent female students in the tenth grade in Muscat Governorate. The body image scale and the group counselling program based on acceptance and commitment therapy were used to achieve the study objective. The program consisted of ten sessions, two sessions per week. The research used the semi-experimental approach in two equal groups, with pre, post, and follow-up tests. Sixteen female adolescent students were involved purposely in the study procedures from the tenth grade, which was distributed equally randomly into two groups, one of them was an experimental group that participated in a group counselling program based on acceptance and commitment therapy, and a control group, which was used for comparison purposes. The results of the study showed that there were statistically significant differences between the average ranks of the scores of the experimental group members in the pre-and post-tests of the body image scale in favor of the post-test. There were statistically significant differences between the average ranks of the degrees of the experimental and control groups in the post-test of the body image scale in favor of the experimental group. The results revealed that the positive effects of the counselling program were sustained after one month follow-up period.