Lumbar artery pseudoaneurysms are infrequent complications of penetrating trauma. When present, they are often accompanied by other injuries; however, we report the case of an isolated traumatic lumbar artery aneurysm resulting from a single knife stab. The lesion was successfully treated with endovascular microcoil embolization. While these injuries are uncommon, the surgeon must maintain a high index of suspicion, even with seemingly uncomplicated injuries, as a missed traumatic pseudoaneurysm may be life threatening.