Background: Neuromuscular electrical stimulation (NMES) is a therapy approach that has been utilised to speed the rehabilitation of individuals with neurological injury. NMES stimulation has been shown to be an effective adjunct in the enhancement of muscle recruitment. Objective: To investigate the effect NMES on shoulder dysfunction after mastectomy operation. Patients and Methods: Sixty-eight female patients with age ranged from 40-55 years, with shoulder dysfunction after mastectomy were participated in this study. They were assigned randomly and equally in two groups. Shoulder range of motion “ROM" was measured pre, after 3 weeks (post 1) and after 6 weeks (post 2) by electronic goniometer. Shoulder dysfunction was assessed by disability of Arm, Shoulder and Hand (DASH) scale; Group A received NMES and exercise program (stretching, strengthening and active ROM exercises) 3 sessions per week for 6 weeks. Group B received exercise program. Results: There was a significant difference in shoulder ROM and dysfunction between pre, post1, and post 2 in group A as P value was (0.001). but there was no significant difference in pre, post1 and post 2 measurements in group B as P value was <0.05.  Conclusion: Neuromuscular electrical stimulation is an effective method for treatment of shoulder dysfunction post mastectomy.