Results exhibited that extracellular OIP5-AS1 was packaged into exosomes, which were secreted by trastuzumab-resistant cells and could be taken up by trastuzumab sensitive cells via exosomes transfer, thereby disseminated trastuzumab resistance to recipient cells in vitro as well as inhibited cytotoxicity induced by trastuzumab in tumor growth in vivo in breast cancer. This evidence concerns the gene OIP5 and breast cancer.