Objective To investigate the effect of radiotherapy after neoadjuvant chemotherapy and modified radical surgery on breast cancer specific survival (BCSS) of patients with stage cT1–2N1M0 breast cancer. Methods A total of 917 cT1–2N1M0 stage breast cancer patients treated with neoadjuvant chemotherapy and modified radical surgery from 2010 to 2017 were extracted from the The Surveillance, Epidemiology, and End Results (SEER) database. Of them 720 matched patients were divided into radiotherapy group (n=360) and non-radiotherapy group (n=360) by using propensity score matching (PSM). Cox proportional hazard regression model was used to explore the factors affecting BCSS. Results Patients were all interviewed for a median follow-up of 65 months, and the 5-year BCSS was 91.9% in the radiotherapy group and 93.2% in the non-radiotherapy group, there was no significant difference between the 2 groups (χ2=0.292, P=0.589). The results were the same in patients with no axillary lymph node metastasis, one axillary lymphnode metastasis, two axillary lymph node metastasis and 3 axillary lymph node metastasis group (χ2=0.139, P=0.709; χ2=0.578, P=0.447; χ2=2.617, P=0.106; χ2=0.062, P=0.803). The result of Cox proportional hazard regression analysis showed that, after controlling for Grade grade, time from diagnosis to treatment, efficacy of neoadjuvant chemotherapy, number of positive axillary lymph nodes, molecular typing, and tumor diameter at first diagnosis, radiotherapy had no statistically significant effect on BCSS [HR=1.048, 95%CI (0.704, 1.561), P=0.817]. Conclusions The effect of radiotherapy on the BCSS of patients with stage cT1–2N1M0 breast cancer who have received neoadjuvant chemotherapy and modified radical surgery with 0 to 3 axillary lymph nodes metastases is limited, but whether to undergo radiotherapy should still be determined according to the comprehensive risk of individual tumor patients.