This study compared the radiographic and clinical outcomes of pediatric diaphyseal femur fractures treated by submuscular plating, flexible retrograde intramedullary nailing, or rigid antegrade intramedullary nailing with a trochanteric entry point in skeletally immature patients who were 8 years and older. A retrospective review was conducted of skeletally immature patients 8 years and older who were treated for femur fracture with submuscular plating, flexible intramedullary nailing, or rigid intramedullary nailing from 2001 to 2014 with a minimum 12-week follow-up. Treatment outcomes were compared for statistical significance, including time to union, malunion, nonunion, heterotopic ossification, avascular necrosis, time to full weight bearing, limb length discrepancy, residual limp, painful hardware, and infection. The study identified 198 femur fractures in 196 patients (mean age, 11.9 years). Each femur fracture was treated with submuscular plating (35), flexible intramedullary nailing (61), or rigid intramedullary nailing (102). Mean follow-up across the cohort was 48 weeks, ranging from 12 to 225 weeks. Flexible nailing was associated with an increased incidence of malunion (P<.0001) and hardware irritation (P=.0204) and longer time to full weight bearing (P=.0018). Rigid nailing was associated with an increased incidence of limp at 12-week followup (P=.0412). Additionally, 23.5% of patients who were treated with rigid nailing had heterotopic ossification. Of all surgical methods, submuscular plating allowed for the most rapid return to full weight bearing (mean, 7 weeks) and offered the fastest healing rate (mean, 6 weeks). Submuscular plating resulted in faster times to union and full weight bearing, with minimal complication rates. Rigid intramedullary nailing with trochanteric entry resulted in a lower incidence of malunion and hardware-related complications; however, these patients had an increased incidence of heterotopic ossification and residual limp postoperatively. Flexible retrograde intramedullary nailing resulted in the highest rates of malunion and hardware irritation and the longest time to full weight bearing. [Orthopedics. 2016; 39(6):353-358.].