Background: Unstable pelvic fractures in children are serious and complex injuries, and the optimal method to manage these injuries is controversial. Hypothesis: We hypothesized that an external fixator would be a satisfactory method of treating unstable pelvic fractures in children. Patients and Methods: We retrospectively reviewed 40 pediatric patients with unstable pelvic fractures who were treated with an external fixator in Beijing Children's Hospital from June 2006 to June 2016. Postoperative follow-up was 12 to 108 months, with an average of 26 months. One year after the operation, fracture healing, pelvic asymmetry, and deformity index were assessed by X-ray. Pelvic function was evaluated with the Cole evaluation standard, and daily cognitive and motor functions were evaluated by weeFIM. Patient complications were recorded. Results: The average age of the 40 patients was 5.9 +/- 3.1 years (2 to 14.5), including 25 boys and 15 girls. Among these cases, 37 (92.5%) had injuries caused by traffic accidents and 3 (7.5%) had injuries caused by falling from height. Based on the Tile classification, there were 18 cases of class B (14 class B2 and 4 class B3) and 22 cases of class C (15 class C1, 6 class C2, and 1 class C3). The X-rays showed good fracture healing at the 1-year postoperative follow-up. The pelvic asymmetry was reduced from 1.13 cm before the operation to 0.88 cm after (p < 0.05), and the deformity index was decreased from 0.09 before to 0.05 after the operation (p < 0.05). At the 1-year postoperative follow-up, 36 patients had excellent Cole scores, and 4 had good Cole scores, with a good or excellent rate of 100%. According to the weeFIM, 28 patients had complete independence, 11 had basic independence, and 1 had conditional independence. Three patients (7.5%) had complications, all of which were postoperative pin-site infections. Discussion: For children with horizontally unstable pelvic fractures, an external fixator can be used alone. For children with horizontally and vertically unstable pelvic fractures, after external fixator placement and reduction, lower extremity traction can be performed to achieve better reduction and maintain stability, and the therapeutic effect is satisfactory. (C) 2021 Elsevier Masson SAS. All rights reserved.