Background: The survival benefit of adjuvant chemotherapy in breast cancer is well established. However, the optimal timing to initiation of chemotherapy after definitive surgery is unknown. We evaluated the association between time to initiation of chemotherapy and survival outcomes according to breast cancer subtype and stage at diagnosis. Methods: Women diagnosed with stage I–III breast cancer between 1997-2011 who received adjuvant chemotherapy at our institution were included. Patients were categorized according to time from definitive surgery to adjuvant chemotherapy into one of three groups: ≤ 30 days, 31–60 days and more than 60 days. Descriptive statistics, Kaplan-Meier statistics and Cox proportional hazards models were used. Results: Among the 6,827 patients included, the 5-year Overall Survival (OS), Relapse-Free Survival (RFS) and Distant Relapse-Free Survival (DRFS) estimates were similar for the different time-to-chemotherapy categories. Among patients with stage I, there was no association between outcome and time to initiation of chemotherapy. Patients with stage II disease experienced an 18% and 22% increase in risk of RFS (HR 1.18; p=0.038) and DRFS (HR 1.22; p=0.02), when systemic treatment was started >60 days from surgery. Patients with stage III disease that started adjuvant chemotherapy >60 days after surgery had a 70% increase in the risk of death (HR 1.7; p=0.002), a 32% increase risk of relapse (HR 1.32; p=0.046) and a 34% increase risk of distant relapse (HR 1.34; p=0.044). Time to chemotherapy did not have a significant effect on outcome among Hormone Receptor (HR)-positive patients. Patients with triple negative (TNBC) and HER2-positive tumors treated with trastuzumab who started chemotherapy >60 days after surgery had lower 5 year-OS estimates (HR 1.52; p=0.016 and HR 2.62; p=0.005, respectively). Conclusions: Time to chemotherapy did not influence survival outcomes in the overall population. However, patients with stage III, TNBC and HER2-positive tumors treated with trastuzumab, experienced worse outcomes when chemotherapy was delayed. Among patients with tumors with aggressive biology and more advanced stages at diagnosis, early initiation of therapy should be favored.