We present herein a rare case of mediastinal cavernous hemangioma in a 5-year-old boy. The patient was referred to our hospital for an evaluation of cough and high fever. On admission, a chest computed tomogram and magnetic resonance imaging revealed a large tumor arising from the left-sided mediastinum which compressed the left main pulmonary artery and left lung. The tumor, measuring 105 x 60 x 60 mm in size and weighing 170 g, was completely resected without any major bleeding, and a pathological examination confirmed the diagnosis of cavernous hemangioma.