In the present study, we found that UCP2 was a marker of good prognosis in BC and correlated positively with CD8+ T cells as well as M1 macrophages, while negatively with M2 macrophages in BC, which suggested that UCP2 may suppress tumor proliferation by regulating CD8+ T cell infiltration and macrophage polarization in BC. This evidence concerns the gene CD8A and breast cancer.