The high rates of aggressiveness, drug resistance and relapse of breast cancer (BC) are mainly attributed to the inability of conventional therapies to equally eradicate bulk differentiated cells and cancer stem cells (CSCs). To improve the effectiveness of BC treatments, we report the in-water synthesis of novel keratin-based nanoformulations, loaded with the CSC-specific drug salinomycin (SAL), the photosensitizer chlorin e6 (Ce6) and vitamin E acetate (SAL/Ce6@kVEs), which combine the capability of releasing SAL with the production of singlet oxygen upon light irradiation. In vitro experiments on BC cell lines and CSC-enriched mammospheres exposed to single or combined therapies showed that SAL/Ce6@kVEs determine synergistic cell killing, limit their selfrenewal capacity and decrease the stemness potential by eradication of CSCs. In vivo experiments on zebrafish embryos confirmed the capacity of SAL nanoformulations to interfere with the Wnt/β-catenin signaling pathway, which is dysregulated in BC, thus identifying a target for further translation into pre-clinical models.