A man in his 60s was diagnosed with esophageal cancer (T3, N0, StageII) and treated with 5-fluorouracil and cisplatin as neoadjuvant chemotherapy (NAC). On day 18 of the second NAC course, the patient developed febrile neutropenia, and a computed tomography (CT) scan showed pneumatosis cystoides intestinalis (PCI) of the ascending and transverse colon, free air around the ascending colon, thickening of the gallbladder wall, pleural effusion, and ascites. Because there were no signs of peritoneal irritation and intestinal perforation was ruled out, conservative treatment was selected. Seven days after PCI was diagnosed, CT showed improvement in PCI and the free air had disappeared, and 26 days after the diagnosis, a subtotal esophagectomy was performed. Observation of the abdomen did not show a thickened wall or stenosis of the ascending or transverse colon. PCI could be treated conservatively, even with free air in the abdominal cavity, by comprehensively assessing not only the imaging but also the physical findings. We were able to perform radical resection of the esophageal cancer without excessive treatment for PCI.