Background: The endoscopic features of early gastric cancer (EGC) arising from the upper third of the stomach (upper body, fundus, and cardia) has not been well studied. If EGC in the upper third of the stomach can be predicted to have invaded the mucosal (M) or submucosal (SM) layer, endoscopic or surgical treatment can be determined. This study evaluated the endoscopic features of EGC in the upper third of the stomach as well as risk factors for SM invasion. Methods: We retrospectively reviewed patients' medical records from a single tertiary hospital (Daejeon) and investigated endoscopic findings and clinical data. Patients with EGC in the upper third of the stomach who underwent surgery or endoscopic resection between January 2016 and April 2022 were included. Logistic regression was used to determine the risk factors of the SM cancer group. Results: In total, 173 patients were enrolled in this study: 94 with SM cancer and 79 with M cancer. Risk factors for SM invasion determined by univariate logistic regression were clubbing of converging folds (OR 6.279, p=0.000), fusion of converging folds (OR 9.179, P=0.000), irregular nodule in the central lesion (OR 2.336, p=0.016), margin with elevation (OR 2.520, P=0.031), and ulceration (OR 9.686, p=0.000). However, in the multivariate logistic regression analysis, only ulceration was identified as a risk factor (OR 6.598, p=0.007). Conclusions: In EGC occurring in the upper third of the stomach, ulceration is a risk factor for SM invasion. Surgical treatment should be considered if this characteristic is present.