Background & Aims: Recent studies have demonstrated the association between mucosal healing (MH) and infliximab (IFX) trough levels (TLs). However, there is limited data regarding the association between transmural healing (TH) and IFX TLs, especially in the pediatric population of Crohn’s disease (CD). Therefore, we aimed to investigate whether TH evaluated by magnetic resonance enterography (MRE) was associated with IFX TLs in pediatric patients with CD. Methods: This retrospective study was conducted at the Department of Pediatrics, Samsung Medical Center. Pediatric CD patients in whom ileocolonoscopies and MRE were performed simultaneously during maintenance IFX treatment were included in the study. MH was defined as a Simple Endoscopic Score for Crohn’s disease (SES-CD) 3 on ileocolonoscopy. TH was defined as wall thickness ≤ 4 mm with the absence of ulcers, edema, contrast hyperenhancement, fat creeping, Comb’s sign, and complications on all ileocolonic segments evaluated by MRE. The association between TH and IFX TL, as well as MH and IFX TL were retrospectively investigated in subjects with available IFX TL results. Results: A total 83 coupled performances of ileocolonoscopy and MRE were conducted in 61 patients (40 males, and 21 females) under maintenance IFX treatment. Among the 83 coupled performances, IFX TL results were available in 62 performances. MH and TH was observed in 58.1% (36/62), and 27.4% (17/62). IFX TLs were significantly higher in those who achieved MH (median 5.8 vs. 4.8, P=0.023), and TH (median 6.0 vs. 4.6, P=0.047). According to receiver operating curve analysis, the optimal IFX TL cut-off for predicting MH was 5.42 μg/mL (AUC=0.67, 95% CI=0.531-0.809, sensitivity 61.1%, specificity 73.1%, P0.001), and 5.72 μg/mL for predicting TH (AUC=0.678, 95% CI=0.509-0.846, sensitivity 81.2%, specificity 68.8%, P0.001). Conclusions: IFX TLs were significantly higher in pediatric CD patients who had achieved TH on MRE. A higher therapeutic range for IFX TLs may be needed when the therapeutic goal is aimed on achieving TH in pediatric CD patients under maintenance IFX.