Tumours of the trigone are rare, representing less than 2.5% of all intracranial tumours. The most common cause in adults is a meningioma. Glioblastoma multiforme of the trigone is extremely rare, with only six cases reported in the literature. We present a case of a glioblastoma multiforme of the trigone presenting in a 57-year-old man with temporal lobe seizures. Imaging revealed a haemorrhagic minimally enhancing mass of the trigone. Histology showed a high-grade malignant glial-derived neoplasm of World Health Organization Grade IV.