A 49-year-old female presented with diffuse leptomeningeal gliomatosis as the initial manifestation of pontine glioblastoma. Magnetic resonance imaging initially revealed diffuse leptomeningeal enhancement caused by metastatic deposits, predominantly along the basal cistern and bilateral sylvian fissures. The primary pontine lesion appeared as hypointense on T₁-weighted imaging and hyperintense on T₂-weighted imaging, but with no enhancement by gadolinium-diethylenetriaminepenta-acetic acid. There was no diffuse enlargement of the pons. The patient died 11 months after the initial presentation. The primary lesion in the pons was histologically confirmed at autopsy. Diffuse enhancement of leptomeningeal dissemination may occur as the initial manifestation of non-enhanced pontine glioblastoma.