Histiocytic sarcoma is an extremely rare tumor in children. It may occur sporadically or in association with other hematological malignancies. It arises most commonly in the lymph nodes but may occur anywhere in the body and clinical presentation is usually with advanced disease. Following tissue diagnosis and staging, management is with chemotherapy though there are no standard regimes. Surgery has been used successfully for local control. This is the first description of the use of peritonectomy and hyperthermic intraperitoneal chemotherapy to treat histiocytic sarcoma. The 4-year-old patient has been disease free for 6 years.