Giant cell tumour (GCT) of bone is a benign aggressive tumour of the bone. It typically presents in persons aged 20 -40 years. It is rare in adolescents and children. In most cases, GCT of bone occurs in the metaphyseal and epiphyseal regions of long bones. However, in children with open physes, GCT of bone may be centered in the metaphysis and may abut the physis. GCT is most commonly found in the distal femur, proximal tibia, and distal radius. It is not reported after treatment of a cancer in childhood. To the best of authors' knowledge, the coexistence of giant cell tumour of the bone and Hodgkin disease has not been reported in the literature. We report an atypical case of giant cell tumour of humerus in a skeletally immature child treated for Hodgkin's disease (HD), which had initially presented as a bone cyst radiologically.