We report a case of a mediastinal seminoma occurring 19 months after the resolution of a pineal germinoma. A 15-year-old boy with headaches and visual changes was diagnosed with a pineal germinoma by biopsy and mildly elevated beta-human chorionic gonadatropin (beta-HCG) in serum and cerebral spinal fluid. Radiation therapy leads to the resolution of his pineal germinoma and normalization of the beta-HCG. A mediastinal seminoma (germinoma) was diagnosed nearly 2 years later because of rising serum beta-HCG. There was no evidence of recurrent central nervous system disease. The patient underwent systemic chemotherapy with the complete resolution of the mediastinal seminoma.