Long bone septic non-union by MRSA (methicillin-resistant Staphylococcus aureus) is always a challenge for the orthopaedic society. Traditional treatment options include distraction osteogenesis methods and vascularised bone grafting. These techniques require a high level of expertise and are frequently involved with a variety of side effects or complications. We present a rare case of ulnar fracture complicated by MRSA infection that led to septic non-union. We treated the septic non union with the technique of induced membrane formation (Masquelet technique). A 33 year old male presented to the outpatient clinic, 2 months after internal fixation of a Gustillo I fracture of the left forearm. There was pus discharge from the operative wound and specimen culture was positive for MRSA. Initially the patient received conservative treatment with antibiotics for a period of one month. However, the patient returned with the same clinical presentation. The patient was then treated with hardware removal of the ulna and debridement of the septic non-union. The formed 5 cm bone defect was filled with cement spacer and the ulnar bone was fixed with external fixation. Eight weeks later, the spacer was removed and the bone gap was filled with autologous cancellous bone graft from iliac crest. Five months after grafting, the patient was reviewed. No clinical or functional problems were noted and osseous consolidation of the ulnar bone was confirmed in plain x-rays. The Masquelet technique is a promising alternative treatment for the management of infected long bone non-unions of the upper extremity.