Higher body mass index (BMI) and diabetes are associated with worse breast cancer prognosis. However, few studies have focused on triple-negative breast cancer (TNBC). The goal of this study is to examine this association in a cohort of patients with TNBC. We retrospectively reviewed 501 consecutive patients with TNBC seen at the Washington University Breast Oncology Clinic. Cox proportional hazard models were used to determine the relationship between BMI and diabetes at diagnosis with overall survival (OS) and disease free survival (DFS). Four hundred and forty-eight patients had BMI recorded and 71 patients had diabetes. The median age at diagnosis was 53 (23-98) years and follow-up was 40.1 months (IQR 25.2-62.9). Baseline BMI and diabetes were not associated with OS or DFS. OS hazard ratios (HRs) for patients who were overweight (BMI 25.0-29.99), with class I obesity (BMI 30-34.99), or BMI ≥35 were 1.22 (CI 0.78-1.91), 0.92 (CI 0.59-1.43), and 1.16 (CI 0.70-1.90), respectively. The HRs for DFS in patients who were overweight, with class I obesity, or BMI ≥35 were 1.01 (CI 0.65-1.56), 0.94 (CI 0.60-1.47), and 0.99 (CI 0.63-1.57), respectively. Similarly, the HRs for diabetics were 1.27 (CI 0.82-1.96) for OS and 0.98 (CI 0.64-1.51) for DFS. Obesity and diabetes did not significantly affect survival for patients with TNBC in this study.