Patients with end-stage renal disease are a challenge for oncologists. Despite the recognised benefit in the overall survival of pembrolizumab in patients with advanced melanoma, data on its safety and efficacy in dialysis patients are scarce. We present a clinical case of an 87-year-old woman on haemodialysis with advanced melanoma treated in the first line with pembrolizumab 200 mg every three weeks. She shows no significant adverse events and a good response to treatment. Although she underwent surgical treatment for two oligoprogressions, the patient maintained treatment with pembrolizumab, now demonstrating a response duration of 20 months. The age and comorbidities in this case, coupled with the lack of robust scientific evidence on the use of immunotherapy in dialysis patients, illustrate the daily complexity of therapeutic decisions in oncology.