BACKGROUND: Femoral shaft fracture is a common fracture in pediatric age group reaching 62% of all fracture shaft femur in children in spite of rapid union rate and successful conservative treatment but some cases need surgical intervention and one of the methods using plate and screw by the lateral approach. AIM: This study aims to compare functional outcome fixation of mid-shaft femur fracture in children by plate and screws between (subvastus lateralis and transvastus lateralis) regarding infection, union, and limitation of knee movement. PATIENT AND METHOD: The study was done on 30 children who had diaphyseal fracture femur in Al-Kindy Teaching Hospital in period (April 2018–April 2020) with 6 months follow-up, and the patient was divided into two groups: Group A first treated by subvastus lateral approach 15 patients and the second group, Group B by transvastus lateral approach 15 patients and follow-up done for them after 2 weeks, 4 weeks, 6 weeks, 3 months, and 6 months. RESULTS: At week 16 of follow-up all patients in Group A had union, while in Group B, 14 of 50 patients had union and one patient had no union and one patient in Group B had an infection when compared to Group A. From 15 patients of Group A, two patients had limitation of knee movement in the 1st month of follow-up then in the 3rd month of follow-up, no patient had limitation of knee joint movement, while five patients had limitation of knee joint movement in Group B in the 1st month of follow-up and one patient had limitation knee joint movement in the 3rd month of follow-up. CONCLUSIONS: The subvastus lateralis approach results better than transvastus lateralis in union.