Retinoblastoma usually presents in children younger than 5 years. To our knowledge, 22 cases of retinoblastoma in adults (older than 20 years) have been reported in the literature. Out of 28 patients with histopathologically proven retinoblastoma seen in our institute, one was the adult. Patients had the endophytic tumor with vitreous seeds. Ultrasonography did not reveal calcification. Immunohistochemistry with neuron-specific enolase was used to confirm the diagnosis in this case. The patient ultimately required enucleation. The diagnosis of retinoblastoma should be considered in cases of the whitish mass lesion in the fundus of an adult.