Purpose: The purpose of the present study is to investigate the impact of postoperative radiotherapy on the survival of young women aged 25-29 years diagnosed with different stages of breast cancer. Methods: We conducted a retrospective cohort study that included young women diagnosed with breast cancer from SEER database. The total analytical sample of the present study (n=4153) was divided into two separate groups; intervention group (n=1814) who did receive postoperative radiation therapy (PORT) and control group (n=2339) who did not receive PORT. Chi square test and Kaplan Meier method had been carried out for statistical analysis. Results: Relative survival rate of the intervention group, estimated by Kaplan-Meier method was found to be (62.9%, CI 95%) for breast cancer stage I, (66.1%, CI 95%) and (58.2%, CI 95%) for stages IIA, and IIB respectively. (30.9%, CI 95%) (54%, CI 95%) and (32.1%, CI 95%) for breast cancer stages IIIA, IIIB, and IIIC respectively and (10.3%, CI 95%) for breast cancer stage IV. Conclusion: Postoperative adjuvant radiotherapy shows a significant positive impact on overall survival of young women diagnosed with breast cancer stages III, and IV (P