Primary malignant melanoma in the bladder is very rare, with only 18 cases having been currently reported. A 65-year-old male patient presented with a 5-month history of gross hematuria. On ultrasonography, an 8.1 x 6.1 cm mass was revealed on the bladder wall. A partial cystectomy was performed. Microscopically, the tumor was composed of atypical, pigmented melanocytes that were positive for S-100 protein and they were negative for human melanoma black-45. Although he underwent supportive therapy, an 8.7 x 5.9 cm mass occupying the prevesical space was noted on a follow-up computed tomography scan 4 months later. Two nodules of the left lower lung and multiple enlarged lymph nodes in the left external iliac chain were also revealed. The patient declined any further treatment. The histogenesis of primary bladder melanoma is uncertain, but an origin from neural crest cells has been proposed. The prognosis for patients with this tumor is still poor despite the availability of several therapeutic options.