A gastric carcinoma with the endoscopic features resembling submucosal tumor (SMT) is rare, and reportedly account for only 0.1% to 0.63% of all resected gastric carcinomas. The preoperative diagnosis of SMT-like gastric carcinoma is challenging, and thus, diagnosis is usually made intraoperatively or postoperatively. Furthermore, mucinous adenocarcinoma is an uncommon histologic subtype of gastric carcinoma characterized as an elevated lesion resembling SMT due to abundant mucin pools in submucosa. Here, we report two cases in which a gastric mucinous adenocarcinoma was mistaken as a SMT.