Thymic haemorrhage in a neonate is an exceedingly rare condition. A case is presented of a neonate presenting at birth with cyanosis, respiratory distress and an anterior mediastinal mass. The radiological findings are demonstrated. After surgical excision and histopathological examination the lesion was found to be spontaneous haemorrhage into normal thymic tissue. Spontaneous thymic haemorrhage should be considered in any neonate developing acute respiratory distress with widening of the mediastinum and pleural effusion on chest radiography. Ultrasound may be used to support the diagnosis.