Rectus sheath hematoma (RSH) presenting as acute surgical abdomen is a rare clinical entity. Failing to establish an early diagnosis will probably result in increased morbidity or unnecessary surgical intervention. We describe herein a case of an 85-year-old woman receiving anticoagulants who presented with typical clinical manifestations of acute surgical abdomen and a slightly palpable abdominal mass. Ultrasonography was inconclusive whereas computed tomography scans demonstrated a large right rectus sheath hematoma associated with hemoperitoneum. The patient was treated conservatively with success. It is therefore concluded that RSH must be considered in any elderly patient on anticoagulant therapy who presents with manifestations of acute surgical abdomen.