The purpose of this study was to assess the prognostic impact of age in patients with triple-negative breast cancer (TNBC). 1,732 patients with primary TNBC were analyzed. Five age cohorts (≤30, 31-40, 41-50, 51-60, and >60 years) at diagnosis were correlated with clinical/pathological parameters. Univariate and multivariate analyses were used to examine the effect of age on disease-free (DFS), distant disease-free (DDFS), and overall survival (OS). In patients with TNBC, increasing age at diagnosis was inversely correlated with tumor grade (P < 0.0001); likelihood of being non-Caucasian (P = 0.0001); likelihood of getting chemotherapy (P < 0.0001); and positively correlated with DFS (P = 0.0003); DDFS (P < 0.0001); and OS (P < 0.0001). The median DFS for patients 31-40 and older than 60 years was 4 years [95 % confidence interval (95 % CI) 2-5] and 8 years (95 % CI 5-14, respectively, P = 0.0003). The DDFS and OS were also statistically significantly shorter for younger patients. In multivariate analysis, tumor size, nodal stage, tumor grade, and age remained significant independent prognostic variables. Clinical characteristics of TNBC differ by age group, patients ≤40 years have poorer survival despite more aggressive systemic therapy.