Intrapericardial foregut cysts are rare, and are usually found serendipitously. An abnormal shadow was incidentally found on a chest X-ray film of a 45-year-old asymptomatic female undergoing a regular check-up. Computed tomography revealed a smooth-walled, left mediastinal cyst (70 × 46 mm) immediately adjacent to the pericardium and left ventricle. We performed video-assisted thoracic surgery, which suggested that the lesion had macroscopically originated from the epicardium. However, the resected cyst was histologically determined to be an intrapericardial foregut cyst. This experience taught us that, while intrapericardial cysts possess the latent possibility of causing sudden death, cardiac failure, or eventual malignant changes, carefully planned and meticulously executed resection, avoiding damage to adjacent organs or vessels, is recommended.