A 70-year-old man was diagnosed with coronavirus disease 2019 (COVID-19) pneumonia. Twenty-six days after admission, he experienced hematemesis despite improvement in his respiratory symptoms. Contrast-enhanced computed tomography revealed edematous stomach wall thickening with neither ischemic findings in the gastric wall nor obstruction of the gastric artery. Emergent esophagogastroduodenoscopy showed diffuse dark-red mucosa accompanied by multiple easy-bleeding, irregularly shaped ulcers throughout almost the whole stomach without active bleeding or visible vessels. The clinical course, including the endoscopic findings, progressed favorably with conservative treatment. COVID-19 pneumonia can present with acute gastric mucosal lesion, which may be induced by microvascular thrombosis due to COVID-19-related coagulopathy.