Triple-negative breast cancer (TNBC), a particularly aggressive cancer, significantly menaces women's health. Recently, a novel form of cell death known as cuproptosis has been identified, with the key gene FDX1 emerging as a potential oncogenic factor. We analyzed the heterogeneity of breast cancer (BC) epithelial cells using available single-cell RNA sequencing (scRNA-seq) datasets. We developed knockdown cell lines in vitro and verified the knockdown efficiency with qPCR. The malignant phenotypes of the cells were assessed through cell counting kit-8, colony formation, Transwell, and scratch healing assays. We also co-cultured the cells with CD8 T cells and evaluated their activation using Transwell, CFSE, lactate dehydrogenase release assay, and enzyme-linked immunosorbent assay. IHC analysis was conducted to reveal the impact of FDX1 on tumor growth in mice. Based on scRNA-seq data, we discovered that in TNBC, epithelial cells were more abundant, and T-cell infiltration was less frequent compared to other subtypes of BC. FDX1 + epithelial cells, which are associated with cuproptosis, were highly enriched in TNBC. The expression of FDX1, a key gene in cuproptosis, upregulated in these cells. This upregulation is essential for sustaining the growth, invasion, and migration of TNBC cells. Co-culture experiments revealed that FDX1 expression could modulate the activation and cytotoxicity of T cells. Tumor growth in mice was largely curbed by the knockdown of FDX1 expression. In TNBC, FDX1 expression aids in the survival and proliferation of cancer cells while dampening the immune response of CD8 T cells.