Objective: This study evaluated the long-term outcomes of a stepped care treatment for pediatric obsessive-compulsive disorder (OCD) and investigated whether response to first-step cognitive-behavioral therapy (CBT) is an important indicator of 3-year outcomes. Method: This study is a part of the Nordic Long-term OCD Treatment Study (NordLOTS), in which 269 children and adolescents were treated with CBT. Nonresponders to CBT were randomized to extended treatment with continued CBT or pharmacotherapy with sertraline. Children’s Yale-Brown Obsessive-Compulsive Scale (CY-BOCS) scores no higher than 15 and no higher than 10 were defined as treatment response and remission, respectively. Participants were assessed 2 and 3 years after first-step CBT. Linear mixed-effects models were used to analyze the outcomes. Results: Intent-to-treat analyses showed a significant decrease in CY-BOCS total score from baseline (24.6) to 3-year follow-up (5.0; p =. 001), with a mean decrease of 5.9 from after treatment to 3-year follow-up. Three years after treatment, 90% (n = 242) of participants were rated as responders and 73% were in clinical remission. The duration of treatment did not influence the symptom level at 3-year follow-up (p =. 998) and no significant difference was found (p =. 169) between the extended treatment conditions. Conclusion: The results suggest that evidence-based treatment for pediatric OCD has long-term positive effects, whether a first step of manual-based CBT or extended treatment with CBT or sertraline. The improvements were maintained, and the symptoms decreased further during follow-up and were, after 3 years, similarly independent of treatment duration and form of extended treatment. Clinical trial registration information: Nordic Long-term Obsessive-Compulsive Disorder (OCD) Treatment Study; www.controlled-trials.com; ISRCTN66385119. © 2019 American Academy of Child and Adolescent Psychiatry