A 77-year-old woman was admitted to a local hospital with a 7-day history of vertigo and nausea, followed by gait disturbance. Magnetic resonance imaging showed extensive brain edema with a hemorrhagic component in the right cerebellum. The lesion was heterogeneously enhanced after administration of contrast medium. The presumptive diagnosis was malignant glioma based on these findings, as well as the presence of mass effect and abnormal enhancement. She was referred to our hospital. However, cerebral angiography did not reveal tumor stain or arterial occlusion, but confirmed corkscrew-like venous collaterals and absence of opacification of the superior petrosal vein (SPV) and superior petrosal sinus. Topography of the brain edema was consistent with the drainage territory of the SPV. These findings suggested that the lesion was vasogenic edema caused by thrombosis of the SPV. The patient was conservatively treated without anticoagulation therapy, and the neurological and imaging abnormalities resolved spontaneously. To avoid unnecessary biopsy, thrombosis of the SPV should be considered in the differential diagnosis of infratentorial lesion mimicking brain tumors. Knowledge of the posterior fossa venous anatomy is essential to achieve the correct diagnosis.