Iliopsoas pseudotumour is a serious complication of haemophilia. We present the case of a 20-year-old male patient with a six-month history of left leg weakness, limitation of movement and wasting of the muscles. Clinically he was diagnosed as having a psoas muscle rhabdomyosarcoma. During a computed tomography (CT) scan-guided Tru-cut biopsy he developed a serious and life-threatening bleeding from a retroperitoneal muscular haematoma. The patient underwent laparotomy prior to his final diagnosis of an Iliopsoas pseudotumour, which is a serious, as well as rare, complication of haemophilia.