Objective To explore the axillary lymph node dissection (ALND) could be safely exempted in younger breast cancer patients (≤40 years of age) who receiving breast-conserving surgery combined with radiotherapy in metastasis of 1–2 sentinel lymph node (SLN) and T1–T2 stage. Methods The data of pathological diagnosis of invasive breast cancer from 2004 to 2015 in SEER database were extracted. Patients were divided into SLN biopsy group (SLNB group) and ALND group according to axillary treatment. Propensity matching score (PSM) method was used to match and equalize the clinicopathological features between two groups at 1∶1. Multivariate Cox proportional risk model was used to analyze the relationship between axillary management and breast cancer specific survival (BCSS), and stratified analysis was performed according to clinicopathological features. Results A total of 1 236 patients with a median age of 37 years (quartile: 34, 39 years) were included in the analysis, including 418 patients (33.8%) in the SLNB group and 818 patients (66.2%) in the ALND group. The median follow-up period was 82 months (quartile: 44, 121 months), and 111 cases (9.0%) died of breast cancer, including 33 cases (7.9%) in the SLNB group and 78 cases (9.5%) in the ALND group. The cumulative 5-year BCSS of the SLNB group and the ALND group were 90.8% and 93.4%, respectively, and the log-rank test showed no significant difference (χ2=0.70, P=0.401). After PSM, there were 406 cases in both the SLNB group and the ALND group. The cumulative 5-year BCSS rate in the ALND group was 4.1% higher than that in the SLNB group (94.8% vs. 90.7%). Multivariate Cox proportional hazard analysis showed that ALND could further improve BCSS rate in younger breast cancer patients [HR=0.578, 95%CI (0.335, 0.998), P=0.049]. Stratified analyses showed that ALND improved BCSS in patients diagnosed before 2012 or with a character of lymph node macrometastases, histological grade G3/4, ER negative or PR negative. Conclusions It should be cautious to consider the elimination of ALND in the stage T1–T2 younger patients receiving breast-conserving surgery combined with radiotherapy when 1–2 SLNs positive, especially in patients with high degree of malignant tumor biological behavior or high lymph node tumor burden. Further prospective trials are needed to verify the question.