Chronic-contained rupture of an aortic aneurysm is a rare subset of ruptured aneurysms. The presentation is unusual, and the diagnosis is frequently delayed. Here, we describe a case of contained rupture of abdominal aortic aneurysm that presented with signs and symptoms of femoral neuropathy. Clinical and radiological findings were initially misinterpreted. The correct diagnosis was formulated belatedly, causing a progressively increased risk of fatal events. Surgical aortic repair was performed and the postoperative course was uneventful. In conclusion, in the presence of a retroperitoneal mass, a diagnosis of chronic-contained rupture of an abdominal aortic aneurysm should be considered.