Introduction:Mature teratomas are subtypes of germ cell tumors that contain tissues from endodermal, mesodermal, and ectodermal germ cell layers[1] . These tumors typically arise from gonads. Mature teratomas in the mediastinum are rare lesions; they are typically detected in the anterior mediastinum which is the most common location of extragonadal germ cell tumors [1, 2] . In addition, most teratoma tumors in the anterior mediastinum arise from the thymus or near thymus parenchyma, and intrapericardial or pericardial arising teratomas are considered extremely rare [2] .Mediastinal teratomas most frequently occur in children and young adults. Patients are usually asymptomatic, but large tumors may present with symptoms of compression [3] . Complete surgical resection is the standard treatment. When adhesion to the surrounding tissues is present, residual tissues could be retained to reduce the injury of the peripheral blood vessels and nerves [4] .Herein, we report a rare mature mediastinal teratoma with adhesions to the pericardium and discuss the diagnostic and surgical challenges.