Background: Breast cancer is a chronic complex disease. Its progression depends partly on the interaction between tumor and immune cells. Whilst immunotherapy is the new promising treatment, many patients with breast cancer acquire resistance. Interferon gamma (IFN-γ) is a pleiotropic cytokine that is primarily released by T cells and natural killer (NK) cells and has always been praised for its antitumor activities. However, IFN-γ may induce different modulations in breast cancer cells that are expressing or not expressing the hormone receptors estrogen and progesterone. Methods: In this study, to examine the effect of IFN-γ on the subtypes of breast cancer in relation to the expression of estrogen and progesterone genes, we performed RNA-sequencing on the triple negative cells MDA-MB231 and ER/PR transfected MDA-MB231 cells (untreated or treated with 100 ng/ml IFN-γ). Various bioinformatics analyses were performed to investigate the affected functional pathways, and immune genes related to the different types of breast cancer cells. Results: The set of differentially expressed genes (DEGs) that are regulated by IFN-γ were unique, and specific to each breast cancer subtype. These unique DEG patterns in hormone-positive cells (GBP3, HLA-DPA1, HLA-DRB1, HLA-E, IL6) and triple negative cells (IFI6, ISG15, CCL5) showed significant but distinct effects on patients’ overall survival as well as noticeable differences in immune modulation and regulation. Conclusions: IFN-γ signaling can differentially affect the pattern of gene expression in breast cancer cells in an estrogen receptor (ER) / progesterone receptor (PR)-dependent manner. IFN-γ treatment of ER+/PR+ breast cancer cells upregulated the expression of genes related to immune cells and showed improved patient prognosis, while TNBC showed negative regulation of the expression of genes related to immune cells and worse patient prognosis.