Purpose: Additional surgery is recommended for patients after a non-curative endoscopic submucosal dissection (ESD) to prevent residual cancer (RC) or lymph node metastasis (LNM). We aimed to evaluate the clinicopathologic characteristics of patients who underwent an additional gastrectomy after a non-curative ESD procedure and identify the risk factors of RC and LNM. Methods: We retrospectively assessed the clinicopathological factors of 73 patients who underwent additional gastrectomy following a non-curative ESD between January 2009 and December 2019 at our center. Results: RC and LNM rates after additional gastrectomy were 9.6% and 8.2%, respectively. Invasion deeper than 500 μm (P = 0.045), positive horizontal resection margin (P < 0.001), and positive ESD margin (P = 0.001) were identified as statistically significant factors in univariate analysis for RC, but not in multivariate analysis. Lymphatic invasion was the only risk factor found to be significant in both univariate and multivariate analyses (P = 0.005 and P = 0.012). Conclusion Additional gastrectomy is necessary to prevent RC or LNM after non-curative ESD. Lymphatic invasion was also associated with LNM in patients who underwent an additional gastrectomy after a non-curative ESD, and in such cases, active treatment is required.