BACKGROUND Adult bronchogenic cysts are rare. Retrogastric bronchogenic cysts are even rarer with only over 30 cases being reported in the English literature. These foregut cysts can be confused with cystic tumors. CASE PRESENTATION We describe the case of a large gastric bronchogenic cyst in an asymptomatic 61-year-old woman who underwent an abdominal computerized tomography as part of a routine follow-up after lumpectomy due to breast cancer. Final diagnosis was made by endoscopic ultrasound fine needle aspiration (EUS-FNA) which led to conservative management of the patient who has remained asymptomatic over the last 8 years. CONCLUSIONS Preoperative diagnosis of adult gastric bronchogenic cyst has been difficult to achieve. Our case highlights the importance of EUS in establishing the definitive diagnosis, enabling just follow-up with repeated imaging studies. The relevant literature is discussed.