We report a rare case of a primary osseous pleomorphic liposarcoma of the distal femur in a 13-year-old boy. Primary liposarcoma of bone is a very rare malignant tumour originating from primitive mesenchymal cells rather than mature adipose tissue. Pleomorphic liposarcoma is the least common of the eight known histological subtypes in the WHO classification. The entity is not previously reported in children. This is the third reported case of pleomorphic liposarcoma of the bone, and the first reported case presenting in adolescence. We describe the computed tomography and magnetic resonance imaging features of this rare bony tumour.