We report the case of a patient with a gastric hamartomatous inverted polyp (GHIP) and discuss the relevant literature. A 65-year-old woman was referred to our hospital because of a slow-growing pedunculated polyp measuring 30mm in diameter, present in the greater curvature of the fundic region of the stomach. It was covered with normal gastric mucosa, and the top was reddish. A biopsy specimen taken from the reddish area;it showed inflamed gastric mucosa with hyperplastic and mildly distorted foveolar glands. Abdominal contrast computed tomography showed a protruding tumor that was unevenly enhanced and contained multiple cystic lesions inside. Endoscopic ultrasonography (EUS, Olympus GIF-UCT260) showed a heterogeneous tumor with multiple anechoic or low-echoic cystic lesions, originating from the second or third layer of the stomach wall. The patient had no clinical symptoms, no family history, and no laboratory data abnormalities. Based on these findings, we diagnosed her with GHIP. As the polyp had shown an increase in size (5mm/5 years) and about 20% of GHIPs were reported to coexist with precancerous or cancerous lesions, we performed endoscopic polypectomy. The tumor was histologically characterized by submucosal growth of hypertrophic glands with cystic dilatation, accompanied by smooth muscle proliferation, branching from the bundles. Thus, the final diagnosis was GHIP. Though GHIP is a rare and basically benign polyp, the rate with gastric cancer was reported to be relatively high. EUS findings are important for the diagnosis and when GHIP is suspected, the lesion requires to be monitored closely. If there are some signs that suggest a malignancy (growth, changes in surface mucosa, etc.), endoscopic en bloc resection or surgical resection should be considered.