Background Metastatic melanoma of the seminal vesicles is a very rare clinical entity and has been reported only once until today in a patient suffering from concomitant HIV infection 12 years ago. Case presentation We report a case of persistent, painless hemospermia in a young Caucasian caused by metastatic malignant melanoma of the right seminal vesicle. The diagnosis was established by magnetic resonance imaging and transrectal ultrasound-guided biopsy. In the subsequent diagnostic workup the primary location of the tumor remained unknown but concomitant pulmonary, hepatic and supraclavicular lymph node metastases have been detected. Despite immediate chemotherapy initiation the patient finally succumbed to his progressive disease six months later. Conclusions Malignant melanoma should be considered as a rare differential diagnosis of hemospermia after common causes have been ruled out.