A 9-year-old boy presented to the pediatric clinic due to intermittent headaches and vomiting for 3 days. Hydrocephalus, but no lesions, was identified through the coronal T1-weighted contrast-enhanced magnetic resonance imaging (a). The results of tumor marker tests were normal, except for a high alpha-fetoprotein level measured in his blood. One milliliter of iohexol injection (Yangzijiang, Jiangsu, China) was administered into the cerebral ventricles via an externally placed ventricular drain, and a computerized tomography (CT) scan was performed approximately 30 min later. This allowed a pineal mass to be identified through coronal CT ventriculography (b). A diagnosis of pineal germinoma was made. The pineal tumor was resected using ventriculoscopy and confirmed on histopathological examination to be a germinoma. Postoperative chemoradiotherapy was received. No recurrence was identified during the 12-month follow-up period. Our patient was preliminarily misdiagnosed as communicating hydrocephalus. The iohexol CT ventriculography, an uncommon diagnostic technique, played a crucial role in his diagnosis and treatment.