Although lumpectomy with oncoplastic breast reduction (OBR) improves cosmetic results and ameliorates symptomatic macromastia, associated complications may delay adjuvant therapy. This was a single-institution, retrospective study of OBRs (2015-2021). A major complication was defined as need for IV antibiotics, and/or operation under general anesthesia. Association of complications with delay to adjuvant therapy (chemotherapy, radiation) was assessed. In total, 282 patients were included. The major complication rate was 3.9%, and overall complication rate was 31.2%. The most common complication was incisional dehiscence (23.4%). Body mass index [BMI >35 (P < 0.0001)], diabetes (P = 0.02), and HgbA1c [>6.5 (P = 0.0002)] were significantly associated with having a major complication. The occurrence of any complication was associated with a delay in time to radiation (median 7 versus 8 weeks, P < 0.001). The occurrence of a major complication was associated with a more meaningful delay to radiation (median 7 versus 15 weeks, P = 0.002). Occurrence of any complication, or a major complication, was not associated with delay to chemotherapy. The overall complication rate observed after OBR falls within the range reported in the literature. Patients with a BMI more than 35, diabetes, and/or HgbA1c more than 6.5 were at increased risk for a major complication, which was associated with a meaningful delay to radiation. Consideration may be given to partial mastectomy alone without oncoplastic reduction in patients with small tumors when the priority to avoid radiation delay is high (eg, high-risk tumors), or the risk of delay is high (eg, diabetic or BMI >35).