Fulminant, necrotizing colitis is a frequent, and generally fatal, complication of severe granulocytopenia, occurring during the treatment of hematological malignancies. In these cases, the patient complains of severe peritonitis, including nausea, vomiting, abdominal pain, diarrhea or melena, and a high temperature. Here, a rare case of anticancer chemotherapy-induced diffuse necrotizing enterocolitis throughout the entire intestinal tract is presented, which developed in a patient who did not have a hematologic malignancy but who had colon cancer, the only clinical symptom of which was watery stools, without any evidence of peritoneal irritation. Full attention should be paid to progressive diarrhea in patients with malignancies during anticancer chemotherapy.