Gastric duplication cyst is a very rare gastrointestinal tract malformation that accounts for 2%-4%of alimentary tract duplications.Most cases are diagnosed within the first year of life,following presentation of abdominal pain,vomiting,and weight loss and clinical discovery of an abdominal palpable mass.This case report describes a very uncommon symptomatic gastric duplication cyst diagnosed for the first time in adulthood.Only a few other case reports of similar condition exist,and all were identified by endosonography.The current case involves a 52-year-old male who presented with a onemonth history of progressive iron deficiency anemia without overt gastrointestinal bleeding.The patient underwent esophagogastroduodenoscopy,which revealed a 2.0 cm pinkish subepithelial lesion,suspected to be a gastrointestinal stromal tumor(GIST)and source of gastrointestinal bleeding.The endosonography showed inhomogeneous hypoechoic lesions with focal anechoic areas arising from a second and third layer of the gastric wall.Differential diagnoses of GIST,neuroendocrine tumor,or pancreatic heterotopia were made.The lesion was removed using an endoscopic submucosal resection technique.Histopathology revealed an erosive gastric mass composed of a complex structure of dilated gastric glands surrounded by fibro-muscular tissue,fibroblasts,and smooth muscle bundles,which led to the diagnosis of gastric duplication. Gastric duplication cyst is a very rare gastrointestinal tract malformation that accounts for 2% -4% of alimentary tract duplications. Most cases are diagnosed within the first year of life, following presentation of abdominal pain, vomiting, and weight loss and clinical discovery of an abdominal palpable mass.This case report describes a very uncommon symptomatic gastric duplication cyst diagnosed for the first time in adulthood. Of a few other cases reports of similar condition, and all of the identified by endosonography. current case involves a 52-year- old male who presented with onemonth history of progressive iron deficiency anemia without overt gastrointestinal bleeding.The patient underwent esophagogastroduodenoscopy, which revealed a 2.0 cm pinkish subepithelial lesion, suspected to be gastrointestinal stromal tumor (GIST) and source of gastrointestinal bleeding. endosonography showed inhomogeneous hypoechoic lesions with focal anechoic areas arising from a second and third layer of the gastric wall. Differential diagnoses of GIST, neuroendocrine tumor, or pancreatic heterotopia were made. The lesion was removed using an endoscopic submucosal resection technique. Histopathology revealed an erosive gastric mass composed of a complex structure of dilated gastric glands surrounded by fibro- muscular tissue, fibroblasts, and smooth muscle bundles, which led to the diagnosis of gastric duplication.