A case of adenocarcinoma arising in Meckel's diverticulum in a 55 year old man is reported, and a brief review of the literature is presented. The patient developed low abdominal pain and showed elevation of serum carcinoembryonic antigen (CEA) level. The tumour was located in the apical portion of the diverticulum and extended into the mesenterium. Histologically, the tumour was a well‐differentiated adenocarcinoma arising in the Meckel's diverticulum. Immunohistochemical study showed that malignant cells were positive for CEA. The noteworthy feature of this case is the pre‐operative elevation of serum CEA level and the immunohistochemical demonstration of CEA in the cancer cells.