Here we report a case of advanced gastric cancer seen after total proctocolectomy for an early colon cancer associated with ulcerative colitis (UC). A 42-year-old man, diagnosed with UC at the age of 21, had undergone total proctocolectomy at the age of 38 for an early ascending colon cancer. Three years later the patient developed tarry stools and epigastric discomfort. Laboratory data showed anemia together with elevated serum p53 antibody. Gastric endoscopy showed thickening folds around a lesion in the stomach body. The pathological diagnosis was poorly differentiated adenocarcinoma with signet-ring cell carcinoma. Total gastrectomy was performed and the resected specimens showed a diffuse infiltrating tumor (scirrhous gastric carcinoma), 11 × 15 cm in size, with multiple lymph node metastases. Histopathological examination revealed diffuse infiltration of cancer cells throughout the gastric wall and invasion of the serosa. Results of cytology on abdominal lavage were positive for cancer cells. Likewise, immunohistochemical staining showed gastric mucin phenotype cancer cells positive for p53. In conclusion, it is important to bear in mind that patients with UC, especially chronically active pancolitis, potentially bear the risk of upper gastrointestinal complications.