Vascular abnormalities in neurofibromatosis type 1 (NF-1) are rare but sometimes fatal. We report a case of spontaneous rupture of a left renal artery aneurysm in a patient with NF-1. A 41-year-old nonpregnant normotensive woman known to have NF-1 presented to our emergency department with left flank pain. Computed tomography showed a large retroperitoneal hematoma due to left renal artery aneurysm rupture. She was treated with selective transcatheter coil embolization and fully recovered.