We herein report a case of an idiopathic intramural hematoma in the gastric wall that presented with symptoms of anemia. Esophagogastroduodenoscopy revealed a submucosal tumor-like lesion on the anterior gastric wall below the gastric fundus. Noncontrast-enhanced ultrasonography showed an anechoic area with indistinct boundaries mainly located within the submucosal layer in the gastric wall, and the lesion showed no contrast enhancement on contrast-enhanced ultrasonography. Based on a comprehensive analysis of the above-mentioned ultrasonographic imaging findings, a final diagnosis of idiopathic intramural gastric hematoma was made. The patient was treated conservatively, and changes in the size and internal ultrasonographic characteristics of the mass were followed up by ultrasonography. Six months later, esophagogastroduodenoscopy confirmed that the mass had disappeared.