Primary intracranial germinoma is a rare central nervous system tumor that usually arises in the pineal and the supra-sellar region. Here, we report a rare case of primary intracavernous sinus germinoma with an atypical extension pattern, with a comparison to germinomas originating from the cavernous sinus as described in the existing literature. A 12-year-old boy was admitted to our hospital with the chief complaint of the left-side ptosis and double vision. Magnetic resonance imaging showed homogenous enhanced mass lesion in the pineal region together with mass lesions in the lateral ventricle, left cavernous sinus, and temporal lobe, extending into the left masticator space. The enhanced mass in the intracavernous sinus originated from the cavernous sinus. Endoscopic third ventriculostomy and tumor biopsy was done. Pathological diagnosis was pure germinoma. After six courses of chemotherapy followed by radiation therapy, all the lesions decreased in size significantly. Only faint enhancement around the masticator space remained. We report a rare case of a germinoma that developed mainly in the cavernous sinus with additional tumor masses in the pineal region, ventricles, and tem