This report describes a ruptured internal iliac artery aneurysm that presented as a rectus sheath hematoma (RSH). The patient developed abdominal pain and a large, tense lower abdominal wall mass without peritoneal signs. Computed tomography scan demonstrated a massive RSH contiguous with a ruptured left internal iliac artery aneurysm. Hypovolemic shock prompted immediate laparotomy, aneurysmorrhaphy of the ruptured aneurysm, and evacuation of the rectus hematoma. This uncommon presentation of internal iliac aneurysm rupture should caution against a simple diagnosis of "spontaneous" RSH in a patient with a potentially ruptured iliac aneurysm.