Thymolipomas are rare benign tumours, constituting one of the differential diagnoses of an anterior mediastinal mass. These tumours may run an indolent, asymptomatic course, often achieving massive dimensions before presentation. Once symptomatic, respiratory symptoms predominate. Diagnosis should be confirmed radiologically during the pre-operative work-up, with pathognomonic features demonstrated on both computed tomography (CT) scan and magnetic resonance imaging (MRI). Open surgical resection remains the treatment of choice for lesions of a significant size, and sternotomy is well tolerated in the paediatric population.