Triple-negative breast cancer (TNBC) has a high recurrence risk and poor clinical outcomes. Associations between metabolic syndrome (MetS) risk components and mortality in postmenopausal women with TNBC were examined in the Women’s Health Initiative. Five hundred forty-four postmenopausal women were diagnosed with nonmetastatic TNBC. Baseline risk components included a high waist circumference (≥88 cm), high blood pressure, hypercholesterolemia, and diabetes. Groups were categorized by the number of MetS risk components: none, 1 or 2, or 3 or 4. Hazard ratios (HRs) and 95% confidence intervals (CIs) across groups were computed with multivariable adjusted Cox models. Outcomes included breast cancer-specific mortality and breast cancer overall mortality (breast cancer followed by death from any cause). Variables in the multivariable model included age at TNBC diagnosis; race/ethnicity; income; education; clinical/observational trial status; history of oral contraceptive, hormone, and/or statin use; cancer stage; and chemotherapy and/or radiation treatment status. Of the 544 participants with TNBC, 33% had no MetS risk components (n = 178), 59% had 1 or 2 risk components (n = 323), and 8% had 3 or 4 risk components (n = 43). After a median follow-up from diagnosis of 8.3 years, multivariable results showed that women with 3 or 4 risk components had a nonsignificantly higher risk of breast cancer mortality (HR, 2.05; 95% CI, 0.94-4.47 trend P = .114) and a significantly higher risk of overall mortality (HR, 2.13; 95% CI, 1.22-3.71; trend P = .006) versus women with 0 risk components. Postmenopausal women with TNBC and 3 or 4 MetS risk components have a nonsignificantly higher breast cancer mortality risk and a significantly higher overall mortality risk, likely because of negative influences of metabolic risk factors on several causes of death.