Hepatic portal venous gas (HPVG) is rare with high mortality. There are few reports on HPVG's association with appendicitis. Here we report a case of HPVG associated with appendicitis. Case presentation: A 79-year-old man presented with acute abdominal pain. Physical examination suggested peritoneal irritation. Blood tests indicated acute inflammation, metabolic acidosis, renal dysfunction and disseminated intravascular coagulation. Contrast-enhanced abdominal computed tomography revealed HPVG, a contrast defect in the small intestine, and minor ascites around the intestine. Urgent laparotomy was performed as intestinal ischemia was suspected. There were no findings of intestinal ischemia, but the appendix was discolored with wall thickening. We confirmed a clinical diagnosis of peritonitis caused by gangrenous appendicitis. We performed appendectomy and abdominal drainage. After surgery, the patient needed intensive care for septic shock. He left the ICU 7 days after the surgery and was discharged 10 days later. Conclusion: Thus, appendicitis may cause HPVG.