Children's femoral shaft fractures are commonly treated with flexible intramedullary nailing after closed or open reduction, but there is little information concerning indications for open reduction. The purpose of this study was to determine radiographic and clinical features likely to lead to open reduction before flexible intramedullary nailing. Record review identified 158 femoral shaft fractures treated with flexible intramedullary nailing. In addition to patient demographics and mechanism of injury, data obtained included surgeon name, estimated blood loss, type of reduction, type and diameter of nail, type of operating table, the use of percutaneous reduction techniques or supplemental casting, time to and duration of surgery, total time in operating room, and time to union. Fracture ratios were calculated based on established radiographic protocol. Of 158 fractures, 141 were treated with closed reduction and 17 with open reduction. The anteroposterior fracture index (1.3 ± 0.4, P = 0.0007), surgeon (P = 0.002), and flattop operating table (0.05) were associated with open reduction. Smaller lateral diameter of bone at the fracture site, transverse fracture, and surgeon were all found to be independent risk factors for open reduction; patient characteristics, including age, sex, and BMI, did not seem to influence the choice of open reduction. Fractures with a lower fracture index or pattern resembling a transverse fracture rather than oblique or spiral had an increased risk of converting to an open reduction. Surgeon preference and use of flattop tables also had a significant influence on how the fracture was treated.