Incidental gastrointestinal subepithelial mass is increasing with national cancer screening endoscopy. Most of gastrointestinal subepithelial mass are small-sized and asymptomatic tumor with benign nature, but gastrointestinal stromal tumor should be ruled-out because of its malignant behavior. Although conventional endoscopy alone can differentiate the nature of subepithelial mass, more accurate diagnosis can be achieved with endoscopic ultrasonography and its guided biopsy. In this review, differential diagnosis and treatment strategy of incidental gastrointestinal subepithelial mass would be presented.