Introduction: Trastuzumab is now increasingly being used as a potent HER2 inhibitor in treating breast cancer, while acneiform rashes sometimes arise as skin-related side effects in patients undergoing treatment with HER2 inhibitors, and their specificity as drug-induced eruptions makes their management quite challenging. Pulsed dye laser (PDL) therapy has been utilized to treat a wide variety of vascular lesions, achieving excellent outcomes. Case Report: A 595 nm PDL was used to treat a 38-year-old woman suffering from an acneiform rash induced by trastuzumab as neoadjuvant therapy for breast cancer. One-half of the face received PDL treatment, while the other half served as the control. Conclusion: After just one PDL treatment, the skin lesion demonstrated a remarkable improvement, with a significant reduction in erythematous papules and inflammatory pustules, as well as an improvement in skin thickening. PDL therapy might offer an effective alternative for managing acneiform rashes induced by trastuzumab.