Chemotherapy resistance is a leading cause of treatment failure in breast cancer, often due to mechanisms like the overexpression of multidrug transporters that enhance drug efflux and reduce efficacy. Recent studies suggest that thyroid hormones (THs) may influence tumor processes through integrin αvβ3, their membrane receptor. However, the exact role of THs in modulating chemotherapy response and the underlying mechanisms are still unclear. The aim of this study was to investigate the impact of physiologic concentrations of THs on chemotherapy response in MDA-MB-231 triple negative breast cancer (TNBC) cells in vitro. Our results demonstrate that THs activate integrin αvβ3-dependent signaling pathways, including PI3K-AKT and MAPK, in these cells. Notably, cell viability assays showed that THs attenuate the efficacy of the chemotherapeutic agents Doxorubicin (DOX) and Paclitaxel (PTX). This effect was inhibited by cilengitide, an αvβ3 integrin inhibitor, thus indicating that THs’ modulation of chemotherapy response is mediated by integrin αvβ3. Subsequently, we investigated whether THs could activate mechanisms associated with chemotherapy resistance and found that THs increase the expression and activity of ABC-type transporters. Additionally, the treatment of this cell line with increasing doses of DOX led to the development of resistant clones that were not only resistant to DOX but also to PTX, which was associated with increased expression of multidrug transporters. Finally, we also found that THs could further enhance the expression of these proteins, including MDR1 and BCRP, in DOX-resistant cells. In conclusion, our study shows that THs significantly influence chemotherapy response in TNBC by activating integrin αvβ3 signaling pathways and promoting resistance mechanisms, which could have implications for improving therapeutic strategies in TNBC.