A 7-month-old girl with a white pupil in the right eye is diagnosed with group D retinoblastoma in the right eye and group B retinoblastoma in the left eye. Her right eye is treated with intra-arterial chemotherapy with melphalan, carboplatin, and topotecan. Her left eye was treated with laser photocoagulation. Both eyes achieved tumor regression and were stable after 3 years of follow up. Genetic testing revealed a variant mutation of the RB1 gene, consistent with a hereditary pattern of mosaicism. Her twin sister did not show any signs of disease and had negative genetic testing.