A retrospective review of 60 diaphyseal tibia fractures (31 closed and 29 open fractures) treated with flexible intramedullary fixation was conducted. All charts and radiographs were reviewed. Children ranged in age from 5.1 to 17 years. Fifty patients with 51 fractures were followed up until union and comprised the study group. The mean follow-up period for these 50 patients was 79 weeks. Forty-five fractures achieved bony union within 18 weeks (mean, 8 weeks). Five patients (11%) had delayed healing (3 had delayed unions that ultimately healed with casting or observation, and 2 had nonunions that required secondary procedures to achieve union [1 patient underwent a fibular osteotomy, and 1 underwent exchange nailing with a reamed tibial nail]). These 5 fractures ultimately healed, with a mean time to union of 41 weeks. Patients with delayed healing tended to be older (mean age, 14.1 years) versus the study population as a whole (mean age, 11.7 years). In addition to delayed union, other complications were observed in the study population. One patient healed with malunion (13-degree valgus), requiring corrective osteotomy. One patient with a grade II open fracture was diagnosed with osteomyelitis at the fracture site after attaining bony union. Two patients developed nail migration through the skin, requiring modification or nail removal. The fixation of pediatric diaphyseal tibia fractures with titanium elastic nails is effective but has a substantial rate of delayed healing, particularly in older patients.