Immunotherapy with immune checkpoint inhibitors (ICIs) may be considered as a treatment option for various types of tumors, but the transplant recipient population as well as patients requiring long-term systemic immunosuppression for other reasons have been systematically excluded from clinical trials involving ICIs. We report a case of successful treatment with ICI in a liver transplant recipient diagnosed with a rare subtype of melanoma. This patient had not required any modification to her antirejection immunosuppression before or during immunotherapy, had not experienced any serious immune-related adverse event, and had a durable objective response for nearly 1.5 year now. A summary of a literature review on other case reports is included to show that ICIs can be safe and provide clinically meaningful benefit in transplant patients, although acute rejection and graft loss remain a significant risk. Given the serious complication of graft failure, a detailed discussion of risks and benefits with immunotherapy needs to be made for an informed consent. Nevertheless, transplant recipients with cancer should not be deprived of this potentially life-saving or life-prolonging treatment, and inclusion of this population in future clinical trials should be considered.