A gastric carcinoma with the endoscopic features resembling a submucosal tumor (SMT) is rare, and reportedly accounting for 0.1% to 0.63% of all resected gastric carcinomas in Japan. A diagnosis of a SMT-like gastric carcinoma is often difficult as the tumors are almost entirely covered with normal mucosa. Furthermore mucinous gastric adenocarcinoma is uncommon histologic subtype of gastric cancer. These tumors are detected mostly in an advanced stage and rarely in an early stage. Early mucinous gastric adenocarcinoma is characterized as an elevated lesion resembling SMT due to abundant mucin pools in the submucosa. Here we report one case of SMT-like mucinous gastric adenocarcinoma, diagnosed by the usual endoscopic biopsy and treated with surgery.