BACKGROUND: Nivolumab, the anti-programmed cell death protein 1 antibody, has been approved for advanced melanoma, mainly based on evidence from Western countries. The profile of melanoma differs between Caucasian and Asian patients. This study was performed to obtain post-marketing data of nivolumab in Japanese patients with advanced melanoma. METHODS: This prospective, observational study involved patients with unresectable or metastatic melanoma treated with nivolumab at dosages of 2 mg/kg every 3 weeks or 3 mg/kg every 2 weeks. The primary endpoints were objective response rate and overall survival. The secondary endpoints were progression-free survival and the objective response rate according to immune-related Response Evaluation Criteria in Solid Tumours. RESULT: Among 124 patients analysed, mucosal melanoma was the most common subtype, followed by acral lentiginous, nodular, superficial spreading and lentigo maligna melanoma. Response Evaluation Criteria in Solid Tumours evaluation showed an objective response rate of 17.7%. The median survival time was 15.93 months, and the 1-year overall survival rate was 66%. Outcomes were not significantly different among melanoma subtypes. Better overall survival and/or progression-free survival but not objective response rate were associated with performance status 0, lower levels of lactate dehydrogenase, C-reactive protein and neutrophil-to-lymphocyte ratio. Patients with immune-related adverse events showed a better objective response rate, 3-month landmark overall survival and progression-free survival than patients without immune-related adverse events. CONCLUSION: The objective response rate and median survival time in Japanese patients treated with nivolumab were lower in daily practice than the >30% and >30 months, respectively, seen in global phase III trials. The occurrence of immune-related adverse events may be a predictor for survival and response to treatment with nivolumab.