PURPOSE: This is a retrospective study to analyze the results of unreamed intramedullary nailing in grade III tibial open fracture. MATERIALS AND METHODS: Twenty-nine Gustilo-Anderson grade III tibial open fractures fixed with unreamed tibial nail were followed more than one year. Primary union rate, union time, infection, conversion to external fixation, ankle and knee function according to different grade of open, fracture level, AO classification, and muscle flap were evaluated. RESULTS: Primary union was achieved at sixteen fractures. There were three delayed union that achieved union twenty week after primary operation. And eight undergone secondary bone grafts which were done after inflammation sign subcided. Complications about infection were in five cases. Two cases were unable to maintain internal fixation due to deep infection, and three of superficial infection were treated with repeated debridement and antibiotics use. CONCLUSION: In grade III tibial open fracture, unreamed nailing with early soft tissue reconstruction and early prophylactic bone graft can be a good treatment.