A 60-year-old woman was admitted for the treatment of a gastric neuroendocrine tumor (NET) associated with type A chronic atrophic gastritis. The lesion measured 10 mm in diameter, and a computed tomography scan did not reveal any metastatic lesions. Endoscopic submucosal dissection (ESD) was subsequently performed. A histological examination revealed three gastric NETs, two of which exhibited vessel invasion. Endocrine cell micronests associated with a high risk of recurrence were also observed. Therefore, the patient underwent total gastrectomy with lymph node dissection. Because vessel invasion can occur in patients with small gastric NET G1, the use of ESD should be considered to carefully estimate the presence of invasion.