The authors report the first case of vasogenic cerebral edema due to a cell-mediated hypersensitivity reaction to a nickel-containing aneurysm clip. The patient initially presented for elective clipping of a right middle cerebral artery aneurysm, and on long-term follow-up she demonstrated relapsing-remitting cerebral edema. Four years post–aneurysm clipping, she underwent an exploratory craniotomy given unsuccessful conservative management of her headaches and imaging evidence of cerebral edema with mass effect. During surgery, gross parenchymal edema and inflammatory nodules were observed. Histopathology was consistent with a cell-mediated (Type IV) hypersensitivity reaction. Concerns regarding nickel allergy are often reported in the cardiac literature. This case highlights the possibility of nickel hypersensitivity when using nickel-containing aneurysm clips, especially in patients with known nickel allergies.