We report an 80-year-old man who presented with non-islet cell tumor hypoglycemia (NICTH) in association with hepatic recurrence of gastric cancer. His serum potassium was reduced from 3.9 to 3.1 mmol/l 5 weeks after gastrectomy, and he subsequently developed hypoglycemic coma. He was diagnosed as having NICTH because of the presence of serum big IGF-II and positive staining for IGF-II in gastric cancer cells obtained at surgery. A computed tomography showed multiple liver metastases. His hypoglycemia was refractory to steroid therapy. This case suggested that NICTH could develop in association with hepatic metastases of gastric cancer. Unexpected hypokalemia may be a manifestation of occult NICTH.