Second nonocular malignancies develop with increased incidence in patients with hereditary retinoblastoma. Osteosarcoma is by far the most common type with an incidence of up to 50%, followed by soft tissue sarcomas. Visceral leiomyosarcoma is extremely rare and only 2 cases have been reported in the past 2 decades, one in the liver and another one in the urinary bladder, both of which developed after cyclophosphamide therapy. Here we report a case of vesical leiomyosarcoma that was diagnosed in a 49-year-old woman 47 years after the diagnosis of a hereditary retinoblastoma. The patient's retinoblastoma was treated with unilateral enucleation without adjuvant radiation or chemotherapy. We believe that this is the first report of vesical leiomyosarcoma occurring in a patient with retinoblastoma without a prior history of radiation or chemotherapy. This report is significant not only because of the rarity of vesical leiomyosarcoma as a second nonocular tumor in retinoblastoma patients, but also because of the infrequency of vesical leiomyosarcoma in general. We also investigated the potential molecular pathogenesis of the leiomyosarcoma.