Purpose : The purpose of this study is to investigate an occurrence of valgus deformity of ankle joint after vascularized fibular graft in children. Materials and Methods : Four children under 15 years who were surgically treated with vascularized fibular graft were studied. The age of the patients was from 4 years to 13 years, the follow-up period was from 24 months to 108 months. The causes of vascularized fibular graft were open fracture (1 case), congenital psuedarthrosis (2 cases), hypoplastic ulna (1 case). The tibiofibular synostosis was done in 3 cases and not in 1 case. We measured the tibiotalar angle and bimalleolar angle at immediately postoperative and final radiography, and checked ankle motion, pain, and instability of ankle joint. Results : The A-P mortise angle was not different between initial and final radiography in all cases. The intermalleolar angle increased in all cases at the final radiography. There were no pain, instability and limitation of ankle motion. Conclusion: We consider the tibiofibular synostosis can prevent from ankle valgus deformity after vascularized fibular graft in children.