Trastuzumab has gained a central role in the treatment of HER2-positive breast cancer, revolutionizing care in this setting. However, since the beginning of its use there have been concerns about its cardiac safety. Trastuzumab can give rise to cardiac toxicity, in some cases leading to discontinuation of treatment. Growing evidence shows that trastuzumab toxicity can be detected early or averted by means of new chemotherapy regimens using different anthracycline formulations or avoiding anthracyclines altogether. Moreover, patients in whom cardiac toxicity develops can be treated effectively and full cardiac function can be restored thanks to progress in drug management. Knowing the characteristics and proper management of trastuzumab toxicity is of paramount importance to grant patients in this setting the best available treatment.