Background: The double-blind TERIKIDS study demonstrated the efficacy and safety of teriflunomide. Objective: To evaluate the efficacy, safety, and tolerability of continuous teriflunomide treatment in the TERIKIDS open-label extension. Methods: In the double-blind period, children with relapsing MS were randomized to placebo or teriflunomide (14 mg adult-equivalent dose) for ⩽ 96 weeks. Participants received teriflunomide for ⩽ 192 weeks post-randomization in the open-label extension. Results: The mean age at screening was 14.6 years. For teriflunomide/teriflunomide versus placebo/teriflunomide, estimated clinical relapse risk was reduced by 38% (hazard ratio (HR) 0.62; 95% confidence interval (CI) 0.39–0.98; p = 0.11) and numbers of gadolinium-enhancing T1 and new/enlarging T2 lesions were reduced by 43% (relative risk (RR) 0.570; 95% CI 0.33–0.98; p = 0.043) and 49% (RR 0.511; 95% CI 0.34–0.76; p = 0.001), respectively, in the combined double-blind and open-label periods. There was a trend toward reduced risk of 24-week sustained disability progression for teriflunomide/teriflunomide versus placebo/teriflunomide (HR 0.47; 95% CI 0.23–0.96). During the open-label extension, incidences of safety-related discontinuations were 4.0% (teriflunomide/teriflunomide) and 13.5% (placebo/teriflunomide), including two children who developed pancreatitis in the teriflunomide/teriflunomide group. Conclusion: Teriflunomide reduced the long-term risk of focal inflammatory activity, with generally manageable tolerability and no new safety signals. Further evidence would strengthen clinical efficacy findings. ClinicalTrials.gov: NCT02201108.