Background and objectives: Distraction osteogenesis is one of the discoveries of Ilizarov which can be used to fill the gap in long bones, control infection, stimulate osteogenesis and equalize the limb. A nonunion is said to have occurred once there is clinical and/or radiological evidence of cessation of fracture healing, usually after 6-8 months. A septic nonunion is defined as a nonunion complicated by local infection at the fracture site and in the surrounding tissues. The aim of this study was to evaluate the effectiveness of treating infected nonunion of femoral shaft by using Ilizarov method. Methods: in this prospective case series study, 13 patients with infected gap nonunion of femoral shaft were treated surgically with meticulous debridement and bone transport through application of Ilizarov ring fixator. Results: The mean age was 30.2 years. The mean length of bone loss was 6.1 centimeters. All patients achieved bony union with eradication of infection. The mean external fixation time was 5.9 months with a mean healing index of 1.1 month/ cm. The bone and functional results were evaluated by using Association for the study and application of the methods of Ilizarov (ASAMI) scoring system. The bone results were excellent and good in 84.6%, fair in 15.4% and poor in 0%. The functional results were excellent and good in 77%, fair in 15.4%, poor in 7.7% and failure in 0%. Conclusions:Treatment of infected gap nonunion of femoral shaft by Ilizarov method provides an excellent result if conducted properly with a good patient education, preparation, surgical techniques and patient follow up.