Trastuzumab is the cornerstone treatment for HER2-positive breast cancer. While ocular side effects are more commonly described after the use of the antibody-drug conjugate ado-trastuzumab emtansine, we here describe corneal melting in a 79-year-old patient after three cycles of trastuzumab monotherapy. Signs and symptoms persisted with subsequent trastuzumab cycles. The patient showed improvement after treatment with intense lubrication, topical antibiotics, and topical steroids. After tapering of steroids, there was recurrence of epitheliopathy after subsequent trastuzumab treatment, which subsided upon restarting topical steroids. Finally, the patient was kept on a low-dose topical steroid regimen which prevented further epitheliopathy during the next trastuzumab cycles.