Adrenal venous malformation is an uncommon disease. We report a case of an incidentally diagnosed adrenal cystic mass during an evaluation for gastritis in a child. A 14-year-old girl admitted to our pediatric department for epigastric pain. After the gastroscopy, she was diagnosed with hemorrhagic gastritis. A 5.5 cm-sized cystic mass was incidentally found adjacent to her left adrenal gland during an ultrasound examination for evaluating her abdominal symptoms. She underwent laparoscopic surgery for the diagnosis and treatment of this cystic mass, which was confirmed to be venous malformation at pathologic diagnosis.