A non-traumatic abdominal wall hematoma is rare, and occurs occasionally due to coughing, physical activity, or antithrombotic/anticoagulant therapy. The condition is usually unilateral; however, rare bilateral cases have been reported. Here, we report a rare case of a non-traumatic bilateral rectus sheath hematoma. The patient was a 60-year-old woman who was urgently admitted to our hospital due to the occurrence of pneumonia during postoperative chemotherapy for breast cancer. Because she exhibited disseminated intravascular coagulation, a therapy with antibacterial agents, thrombomodulin alpha, and catecholamines was initiated. During hospitalization, hemorrhagic shock due to hematomas in both rectus abdominis muscles was observed without any discernible cause. Subsequent emergency angioembolization was successful, and abdominal computed tomography performed 3 months after the onset of the rectus sheath hematoma confirmed a reduction in the hematoma size.