The aim of this study was to evaluate the role of platinum-containing chemotherapy for metastatic triple-negative breast cancer (TNBC) patients in terms of the response rate (RR) and progression-free survival. A second aim was to characterize the clinical behavior at the time of relapse of TNBC. We retrospectively analyzed the clinical outcomes of patients with metastatic breast cancer who received taxane-platinum chemotherapy as the first- or second-line treatment, focusing on the TN phenotype. In total, 257 patients with metastatic breast cancer received platinum-containing chemotherapy at Samsung Medical Center from 1999 to 2006. Of these patients, 106 patients with available data on estrogen (ER), progesterone (PgR) and human epidermal growth factor receptor-2 (HER2) receptor status received taxane-platinum regimen as the first- or second-line treatment. The overall RR of patients with TNBC was 39%. This rate did not differ significantly from those of patients with other phenotypes. The time to death after chemotherapy (19 vs. 50 months, p = 0.037) and overall survival (OS) (21 vs. 56 months, p = 0.030) differed significantly between patients with TNBC and non-TNBC. TNBC showed a unique locoregional infiltration pattern at relapse, which might reflect its aggressive clinical behavior. Despite the similar response to platinum-containing chemotherapy, patients with TNBC had a shorter OS than patients with non-TNBC. The implication of TN phenotype as poor prognostic factor is uncertain, because it needs to be defined whether poor outcome is related to the rapid growing characteristics of tumor itself or the resistance to drug therapy. Further prospective studies are warranted.