Background: General incidence of humeral shaft fractures remain in the area to 1% to 2% of all fractures. Shoulder & elbow stiffness, non-union and mal-union are commonly seen with conservative treatment. Open reduction and internal fixation with plate and screws require extensive soft tissue stripping and high rates of radial nerve palsy. An interlocking intra medullary nail system is an effective and less invasive method with fewer complications. The aim of this study is to document the clinical outcome and complications associated with the use of intramedullary interlocking nail in acute diaphyseal fractures of humerus.