The exact role of autophagy in breast cancers remains elusive. In this study, we explored the potential functions of autophagy-related 7 (Atg7) in breast cancer cell lines and tissues. Compared to normal breast tissue, a significantly lower expression of Atg7 was observed in triple-negative breast cancer (TNBC), but not other subtypes. A higher Atg7 expression was significantly associated with favorable clinicopathologic factors and better prognostic outcomes in patients with TNBC. Reflecting the clinical and pathologic observations, Atg7 was found to inhibit proliferation and migration, but promotes apoptosis in TNBC cell lines. Furthermore, Atg7 suppressed epithelial–mesenchymal transition through inhibiting aerobic glycolysis metabolism of TNBC cells. These findings provided novel molecular and clinical evidence of Atg7 in modulating the biological behavior of TNBC, thus warranting further investigation.