Studies on extremely severe elbow stiffness after chronic dislocation in children are scarce. This study aims to investigate the choice of surgical treatment modalities and to analyze their treatment efficacy in children with chronic elbow dislocation with extremely severe periarticular stiffness. Data of 21 children with chronic elbow dislocation with extremely severe periarticular stiffness diagnosed and treated in our department between February 2015 and February 2021 were retrospectively analyzed. Twenty boys and one girl were included in the study, their mean age was 11 ± 2.5 years, and they had concomitant distal humerus fractures. For the treatment protocol, all children with extremely severe elbow stiffness were treated with open arthrolysis, and elbow joint stability was intraoperatively assessed. All children performed passive functional exercises the day after surgery. The elbow flexion and extension angles, range of motion (ROM), and Mayo score were evaluated preoperatively and at the final follow-up. Of the 21 children, only one had recurrent severe stiffness of the elbow joint after surgery; nevertheless, the function was still improved compared with that before surgery. Preoperatively, the mean elbow extension and flexion angles were 72.2° ± 12.7° and 93.6° ± 11.1°, respectively, and the range of motion (ROM) of the elbow joint was 17.8° ± 8.3°. At the final follow-up, the mean elbow extension and flexion angles were 22.7° ± 18.6° and 118.8° ± 15.4°, respectively, and the elbow joint ROM was 96.1° ± 17.4°. The differences in the preoperative and postoperative ROMs, flexion angles, and extension angles of the elbow joint were significant (p < 0.01). The MEPS at the final follow-up was 78.57 ± 14.24, which was significantly higher than preoperative (29.76 ± 10.89), and the excellent rate was 81%. Open arthrolysis and open reduction and internal fixation of the elbow joint are effective in treating chronic elbow dislocation with extremely severe stiffness in children. © 2023 The Authors. Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.