<p>Keratin 15 (KRT15) promotes tumor progression in several cancers, but its engagement in breast cancer is seldom uncovered. This study aimed to explore the impact of KRT15 modification on breast cancer growth, mobility, radiosensitivity, ferroptosis, and Wnt/β-catenin signaling pathway. A lentiviral vector containing short hairpin RNA or complementary DNA targeting KRT15 was transfected into MDA-MB-231 and MCF-7 cells in vitro. The transfected MCF-7 cells were further proposed to irradiation treatment. In vivo, female BALB/c nude mice were used to establish xenograft model with KRT15-overexpressed MDA-MB-231 cells and treated by irradiation. KRT15 overexpression promoted cell proliferation, migration, invasion, colony number, epithelial–mesenchymal transition (EMT, reflected by E-Cadherin, N-Cadherin, and Vimentin expressions), and S-stage cell cycle arrest in MDA-MB-231 and MCF-7 cells, but repressed cell apoptosis and ferroptosis (reflected by DMT1, SLC7A11, FTH1, and GPX4 expressions); while KRT15 knockdown exhibited the opposite effects. Importantly, KRT15 overexpression enhanced irradiation resistance in MCF-7 cells reflected by cell proliferation, migration, invasion, colony number, cell cycle, and cell apoptosis detections. Besides, KRT15 overexpression increased EMT and activated Wnt/β-catenin signaling pathway (reflected by β-catenin, TCF-1, c-Myc, CCND1, MMP7 expressions) in MCF-7 cells with or without irradiation. In vivo experiments further validated that KRT15 overexpression promoted tumor growth, EMT, Wnt/β-catenin signaling pathway, and irradiation resistance, but repressed the ferroptosis. Collectively, KRT15 may facilitate tumor growth, invasion, EMT, and radioresistance but represses ferroptosis in a Wnt/β-catenin signaling-related way, suggesting its potency as a treatment target for breast cancer management.</p>