Pneumatosis intestinalis is a condition characterized by the presence of gas within the wall of the small or large intestine. The causes, clinical features, and prognosis vary among individual cases, and careful assessment is crucial for appropriate treatment. Herein, we describe three cases of pneumatosis intestinalis with different clinical features. The small intestine was involved in two patients, whereas the ascending colon was involved in the third patient. Surgical intervention was chosen in two patients because of severe abdominal pain, decreased base excess, and the presence of portal venous gas (in one patient). However, there were no signs of intestinal necrosis on pathological examination. In the third case, computed tomography revealed free air within the peritoneum. Despite this, the patient was not experiencing any severe abdominal pain or deterioration of vital signs, and was treated successfully with fasting and antibiotics. The third patient was on several medications, such as immunosuppressant, prednisolone for cutaneous malignant lymphoma, and α-glucosidase inhibitor for diabetes mellitus, and the condition was suggested as drug-induced pneumatosis intestinalis.In conclusion, patients with pneumatosis intestinalis present with various clinical features from critical to mild conditions. Some are accompanied by severe signs such as portal venous gas, intraperitoneal free air, and metabolic acidosis, necessitating urgent intervention; contrarily, the other can be managed conservatively. For successful treatment, the evaluation of the severity of the disease and the accompanying conditions such as perforation and necrosis of the intestine is mandatory.