Introduction Increases in disease-free survival and overall survival (OS) with the use of adjuvant chemotherapy in early breast cancer (BC) are widely known; however, the optimal time to initiate treatment with adjuvant chemotherapy remains controversial. Objective To evaluate the time elapsed between surgery and the initiation of adjuvant chemotherapy and its possible impact on OS in patients diagnosed with BC stages I–III. Materials and Methods This retrospective study included 112 patients diagnosed with BC stages I–III who received adjuvant chemotherapy at the Mastology Unit of the Hospital de Clínicas in Uruguay from 2009 to 2019. OS was estimated using the Kaplan–Meier method, and a Cox proportional hazards model was used to estimate hazard ratios (HRs) and 95% confidence intervals. Results No statistically significant association was found between the time from surgery to the initiation of chemotherapy and the described variables. OS was worse for patients initiating chemotherapy more than 90 days after breast surgery (n = 19) (HR 7.63; p = 0.004) and between 61 and 90 days after surgery (n = 46) (HR 4.58; p = 0.040) compared to those who started before 30 days (n = 23). Controlling by type of surgery and stage, the prognosis of patients who started chemotherapy between 61 and 90 days after surgery was similar to that of patients who underwent chemotherapy within the first 30 days, controlling for surgery (HR 4.10; p = 0.056) and controlling for stage (HR 3.76; p = 0.075). Prognosis was worse for patients with stage III disease (p = 0.022) who underwent a mastectomy and/or axillary lymph node dissection (p = 0.025). Conclusion Patients who started chemotherapy more than 90 days following surgery and those with stage III disease or underwent mastectomy and/or axillary lymph node dissection who initiated it between 61 and 90 days had a worse OS. Multiple factors are involved in the time between surgery and the initiation of chemotherapy, and further studies are needed to evaluate which of these factors influence the delay of chemotherapy in order to design strategies to avoid such delays and their negative impact on survival.