PURPOSE: To analyze the patterns of and risk factors for fixation failure after hip nailing in intertrochanteric (IT) hip fractures. MATERIALS AND METHODS: Fourteen patients who sustained a fixation failure after hip nailing for IT hip fractures were enrolled in this study. The mean age at the index surgery was 74.5 years and the mean time to the fixation failure was 6.6 weeks. All of the serial radiographs up to the fixation failure and pre-operative 3-D computed tomography were analyzed. RESULTS: According to AO classification, there were 7 stable fractures and 7 unstable ones. Of the total of 14 cases, 10 showed a comminution of the greater trochanter tip and incomplete anatomical reduction of the medial and anterior cortex at the fracture site. Of the 10 cases with appropriate position of the lag screw within the femoral head, 9 showed a high pertrochanteric fracture (HPF) pattern. The mechanism of the fixation failure was rotation of the femoral head in 7 of 9 cases with HPF and varus collapse of the proximal fragment in 4 of the other 5 cases. CONCLUSION: The HPF pattern, the comminution of the greater trochanter tip, and incomplete reduction of the medial and anterior cortex may be additional risk factors of fixation failure after treating IT hip fractures with hip nailing in.