Background. Different studies indicate a high prevalence of eating disorders in athletes. These disorders represent a severe defect in many areas of life. Eating disorders can lead to changes in consumer or intake of food and significant damage to physical health and psychosocial sports performance. Objectives. The aim of the present study was examining the effects of Cognitive Behavior Therapy (CBT) on the symptoms of Bulimia Nervosa (BN) of the Athletes. Methods. The research method was semi-experimental with pre-test, post-test, and three-month follow-up test. Three hundred athletes of endurance, aesthetics, and weight-based pre-match sports assessed using the Eating Disorder Diagnostic Scale (EDDS) via Structured Clinical Interview (SCID) and found sixteen athletes with BN. Then they assigned randomly to control and experimental groups. Experimental groups received CBT treatment based on Fairburn et al. (2008) protocol (4 steps, 21 sessions during 16 weeks). Twelve weeks after the final session of CBT, all two groups assessed again by EDDS via SCID to follow up on the persistence of CBT. Results. The symptoms of BN is decreased significantly during CBT, but it didn't change in the control group (N2=0.69, f2,28=30.77, p<0.001). On the other hand, the weight of athletes with BN symptoms increased significantly during CBT, but it decreased in the control group (N2=0.5, f1.27,17.78=14.27, p=0.001). Conclusion. The results of the present study confirm the effectiveness of CBT on the improvement of BN symptoms and weight management, as well as its persistence in athletes.