Purpose The current treatment for the majority of femur fractures in patients five years of age and younger is application of a hip spica cast. The J-splint has been shown to be a temporizing treatment that emergency department providers can apply until the child undergoes the hip spica cast placement. The purpose of this study was to determine if J-splints can be utilized as definitive treatment for pediatric femur fractures. Methods A retrospective review was conducted to identify all patients with a femur fracture between the ages of zero and five years. Those treated with a J-splint as definitive treatment were matched 1:3 regarding age and sex with those treated with a hip spica cast. Additional information obtained included mechanism of injury, the time in the emergency department, admission time, and transfer status. Procedural factors such as number of radiographs/fluoroscopy time, sedation time, and length of time in the operating room were also recorded. Follow-up data including factors such as number of follow-up visits, length of follow-up, and complication rates were also assessed. Anterior-posterior (AP) and lateral radiographs were reviewed to assess angulation, translation, and shortening. The radiographic parameters were assessed immediately after cast/splint placement, as well as at each follow-up time point. Mean difference in angulation between the two interventions was established using a repeated measures mixed effects model, adjusted for age and sex. Results Twenty patients were included in the study of which 5 were treated definitevely to a J-Splint. J-Splinting was associated with 4.4° less malangulation on AP radiographs than hip spica casting over the course of follow-up (p=0.0014). There was no significant difference in fracture angulation on the lateral view between the two groups. No major complications were observed in patients treated by either intervention, however patients with hip spica casts experienced a greater number of minor skin complications. No significant loss of alignment was present in either group at final follow-up. Conclusion J-Splints may be an acceptable alternative to hip spica casting demonstrating comparable results in terms of fracture healing while minimizing complications caused by irritation from the immobilization device. The use of a J-splint as definitive treatment for pediatric femur fractures appears to be a comparable intervention to traditional hip spica casting.