Trilateral retinoblastoma is a rare, but well recognized syndrome. These tumors usually occur in the pineal, parasellar, or suprasellar regions several years after successful management of ocular retinoblastomas without evidence of direct extension or distant metastasis. Here we report a case of trilateral retinoblastoma presenting initially with a sellar tumor and with concurrent unilateral retinoblastoma. The patient was a 5-month-old baby girl showing poor eye contact and nystagmus for several days. She had no family history of retinoblastoma. Brain MRI revealed a midline suprasellar tumor without evidence of cerebrospinal fluid seeding or extracranial metastasis. A pathologic diagnosis of retinoblastoma was made for her brain tumor, and a small, intraocular retinoblastoma was detected in the left eye by thorough examination of the fundus. If a retinoblastoma occurs in the midline of the brain, including the pineal and sellar regions, a careful screening to detect any additional retinal tumors should be performed. Moreover, since these tumors are often hereditary and harbor a worse prognosis, the diagnosis has implications for genetic counseling. This is the first report on a case of trilateral retinoblastoma in Korea presented with a sellar mass.