BACKGROUND The treatment modalities for pediatric femoral shaft fractures are determined by their age, weight, and fracture pattern. Rigid intramedullary nailing (RIN) is usually recommended for patients >11 years of age, and elastic intramedullary nailing (EIN) has been used for patients under 10 years. However, little is known about the use of RIN in patients aged 8 to 10 years. We examined the differences in patients with femoral shaft fractures who were treated with EIN or RIN in terms of (1) fracture healing; (2) changes of anatomic parameters; and (3) related complications. METHODS We retrospectively reviewed 54 patients between 8 and 10 years of age, with femoral shaft fractures, who were treated with either EIN or RIN between 2011 and 2020. Lateral trochanteric entry was used for RIN procedure. The mean follow-up period was 26.4 months (range, 6 to 113 mo). There were 17 patients in the EIN group and 37 patients in the RIN group. The mean age at the time of surgery was 1 year younger in the EIN group ( P <0.01). The mean weight of the patient was significantly heavier in the RIN group compared with the EIN group. RESULTS Complete union of the fracture was achieved slightly faster in the RIN group at 3.4 months compared with 3.7 months in the EIN group ( P =0.04). There were no clinically significant changes of the anatomic parameters in either group, including neck shaft angle and articulotrochanteric distance. There was no evidence of avascular necrosis at the time of final follow-up for either group. There were no significant differences in postoperative complications between the groups. CONCLUSIONS RIN using lateral trochanteric entry is a feasible surgical option for femoral shaft fractures in patients 8 to 10 years of age that are heavier than 40 kg or with unstable fracture patterns. METHODS Level III, retrospective cohort study. See the Guidelines for Authors for a complete description of levels of evidence.