Background: Post mastectomy shoulder pain can be severe enough to result in long-term difficulties, disrupt sleep, impair the ability to carry out daily tasks, including using the affected arm, and result in frozen shoulder. Objective: The aim of the current study is to assess the effectiveness of extracorporeal shock wave on shoulder dysfunction post mastectomy. Patients and methods: The study was conducted on 40 patients undergoing mastectomy between the ages of 40 and 65 who experienced shoulder pain and limited range of motion and were randomly split into two equal groups, each with 20 patients. Group A (Study group): For eight weeks, extracorporeal shockwave therapy (ESWT) was administered once a week to 20 patients of females receiving traditional physical therapy three times per week. Group B (Control group): 20 female patients who got only traditional physical therapy three times a week with sham- shock wave once a week for eight weeks were included in this group. Results: There was a significant increase in the measurement of passive range of motion for shoulder abduction, flexion, external rotation and internal rotation in the post-treatment assessments compared to the baseline measurement (P<0.001) and by comparing both groups, there were a statistically significant higher ROM in Group A than Group B (P< 0.001). Also, a significant increase in the measurement of active ROMs for shoulder abduction, flexion, external rotation and internal rotation in the post-treatment assessments compared to baseline measurement (P<0.001). Conclusion: Extracorporeal shock wave therapy is more effective than conventional physical therapy in the treatment of patients with shoulder dysfunction following mastectomy.