Desmoplastic fibroma is a rare, well differentiated, locally aggressive fibrous tumor usually arising from soft tissues, and rarely from bones. Involvement of forearm bones is extremely unusual. We present a large desmoplastic fibroma of right ulna in a 15-year-old male. The tumor was excised with a wide margin, and the bony defect was reconstructed with nonvascular autologous fibular graft. Reconstruction of the olecranon process was attempted using the fibular head and the remaining olecranon. At 2-years followup, there was no recurrence, flexion extension arc of the elbow joint was 40°-130° and there was no restriction of activities of daily living. [ABSTRACT FROM AUTHOR]