We present a child with a rare finding of an extralobar pulmonary sequestration localized in the upper mediastinum. Findings of the prenatal screening enabled early postnatal diagnostic measures that revealed a heterogeneous mass situated next to the thymus. Based on the localization and inconclusive computed tomography images, the preoperative prediagnoses included enterogenic cyst, thymus cyst and teratoma. Intraoperative features of the vascular supply and structure of the mass drew the surgeons' suspicion to extralobar pulmonary sequestration, which was confirmed in the histopathological examination. The scans were reevaluated after the surgery. Surgical management was implemented prior to the occurrence of any symptoms, which led to a positive general outcome. The presented case should raise the awareness of radiologists, pediatric surgeons and other consultants involved in the diagnostic process of mediastinal lesions in children. The rare localization and lack of visualization of a systemic feeding artery can divert suspicion away from extralobar pulmonary sequestration in the preoperative differential diagnosis.