Abstract: Objective To analyze the prognosis of patients with T1-2N1M0 triple-negative breast cancer（TNBC） after modified radical mastectomy with or without postoperative radiotherapy. Methods One hundred and twenty-nine patients diagnosed with T1-2N1M0 TNBC after modified radical mastectomy from Jan. 2004 to Sep. 2010 were retrospectively reviewed. Of whom 61 cases received postoperative radiotherapy and 68 cases did not. The 5-year overall survival（OS）， locoregional recurrencefree survival（LRFS）and diseasefree surviva（DFS） rates of the two groups were observed. The risk factors for LRFS were analyzed in combination with clinical and patholgical features. Results With a median follow-up of 67 months， 27 patients developed locoregional recurrence. The patients treated with radiotherapy had significantly higher LRFS rates（88.5％ vs. 70.6％， P=0.017） as well as slightly higher DFS rates（78.7％ vs. 63.2％，P=0.068）.The 5-year OS rates were 88.5％ and 82.4％（P=0.068）， respectively. The univariate analysis indicated that age， T stage， the number of positive lymph nodes and postoperative radiotherapy were significant influencing factors for LRFS（P＜0.05）. The multivariate analysis showed that no radiotherapy（HR=3.432，P=0.010）and 3 positive lymph nodes（HR=2.915，P=0.020）were independent prognostic factors for LRFS. Conclusion T1-2N1M0 TNBC after modified radical mastectomy patients may benefit from radiotherapy， which significantly improves locoregional recurrence-free survival. The local control rates of patients with 3 positive axillary nodes was worse， so increasing regional lymph node irradiation should be feasible.