Background: Due to the possibility of metachronous recurrence of gastric neoplasia, surveillance gastroscopy is mandatory after endoscopic resection (ER) for gastric neoplasia. However, there is no consensus on the surveillance gastroscopy interval. This study aimed to find an optimal interval of surveillance gastroscopy and to investigate the risk factors for metachronous gastric neoplasia (MGN). Methods: Medical records were reviewed retrospectively in patients who underwent ER for gastric neoplasia in 3 teaching hospitals from June 2012 to July 2022. Patients were divided into 2 groups; annual surveillance vs. biannual surveillance. The incidence of MGN was identified, and the risk factors for MGN were investigated. Results: Among the 1,533 patients, 677 patients were included (annual surveillance 302, biannual surveillance 375). The median follow-up for all patients was 22 (range, 12‒91) months. MGN was observed in 61 patients and metachronous gastric cancer (MGC) in 26 patients, both of which were not significantly different between the annual and biannual surveillance groups (annual vs. biannual: 26/302 vs. 32/273, P=0.989 in MGN; 13/302 vs. 13/373, P=0.582 in MGC). All the lesions were removed by ER successfully. In a multivariate analysis, severe atrophic gastritis on endoscopy was an independent risk factor for MGC (odds ratio 3.8, 95% confidence interval 1.4‒10.1; P=0.008). H. pylori infection was not a significant risk factor in this study. Conclusions: Meticulous observation is necessary for patients with severe atrophic gastritis during follow-up gastroscopy after ER for gastric neoplasia. Annual surveillance gastroscopy might be enough after ER for gastric neoplasia.