Background Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults, with a median survival of 13 months despite surgery and chemoradiation. GBMs are often hypervascular tumors caused by abnormal oversecretion of growth factors such as vascular endothelial growth factor. These angiogenic factors are hypothesized to promote increased blood flow and possibly secondary changes to arterial walls, thus facilitating the formation of flow-related aneurysms. Case Description A 59-year-old woman presented with headaches, confusion, nausea and emesis. Computed tomography and magnetic resonance imaging revealed a hypervascular lesion, likely high-grade glioma, in the right frontal lobe, with a dilated vessel within the tumor. Cerebral angiography demonstrated a flow-related aneurysm on the right frontopolar artery supplying the tumor. The aneurysm was embolized with coils and the patient later underwent craniotomy for near total resection of the lesion without complications. Final pathology returned GBM with dilated vessels noted. Conclusions Hypervascular lesions, such as GBMs, may be associated with flow-related aneurysms on feeding arteries, but aneurysms within the gross tumor are unusual. Although rare, this finding needs to be recognized on preoperative imaging before tumor resection to prevent potentially catastrophic intraoperative complications.