Background: Ustekinumab is an effective therapy for Crohn disease currently approved for adults. Off-label use in the pediatric population is increasing, but its effectiveness in this age group has not been reported. Aims: The aim of the study was to describe real-world experience with ustekinumab at a tertiary care pediatric inflammatory bowel disease (IBD) center. Methods: As part of an ongoing observational cohort study of biologic-treated pediatric IBD patients initiated in October 2014, data on demographics, disease behavior, location and activity, treatment, and surgical history were collected for all patients receiving ustekinumab. Disease activity was assessed using the Harvey Bradshaw index or partial Mayo score. Primary outcome was steroid-free remission at 52 weeks. Descriptive statistics summarized the safety and efficacy outcomes, and univariate analyses were performed to examine associations of clinical characteristics with efficacy. Results: Fifty-two children and young adults initiating ustekinumab were analyzed; 81% Crohn Disease, 8% ulcerative colitis, and 11% IBD-unspecified. Median [IQR] age at induction was 16.8 [14–18] years. Patients were followed for a minimum of 12 months. Most patients (81%) failed >1 anti-TNF, and 37% failed anti-TNF and vedolizumab; 10 patients were biologic-naïve. At week 52, 75% were still on ustekinumab, and 50% (bio-exposed) and 90% (bio-naïve) were in steroid-free remission. Two infusion reactions and neither serious adverse events nor serious infections were observed. Conclusions: Our results suggest that ustekinumab is efficacious and safe in pediatric patients with IBD. Controlled clinical trial data are needed to confirm these observations.