Accessory spleen can be mistaken as a gastric subepithelial mass, and may not be differentiated in CT or endoscopic ultrasonography (EUS). A gastric subepithelial mass was detected on routine endoscopy in a 39-year old woman with history of splenectomy. In subsequent CT and EUS, the subepithelial mass was located on the fourth layer of the stomach. To make a definite diagnosis, EUS-guided fine needle aspiration (FNA) was performed, and a splenic tissue was demonstrated in histologic examination. EUS-guided FNA can be beneficial in the diagnosis of accessory spleen which mimics a gastric subepithelial mass.