BACKGROUND: Butyric acid's effectiveness has not yet been assessed in the pediatric inflammatory bowel disease (IBD) population. This study aimed to evaluate the effectiveness of oral sodium butyrate as an add-on to standard therapy in children and adolescents with newly diagnosed IBD. METHODS: This was a prospective, randomized, placebo-controlled multicenter study. Patients aged 6-18 years with colonic Crohn's disease or ulcerative colitis, who received standard therapy depending on the disease's severity, were randomized to receive 150 mg sodium butyrate twice a day (group A) or placebo (group B). The primary outcome was the difference in disease activity and fecal calprotectin concentration between the two study groups measured at 12 weeks of the study. RESULTS: In total, 72 patients with initially active disease completed the study, 29 patients in group A and 43 in group B. At week 12 of the study, the majority of patients achieved remission. No difference in remission rate or median disease activity was found between the two groups ( = 0.37 and 0.31, respectively). None of the patients reported adverse events. CONCLUSIONS: A 12-week supplementation with sodium butyrate, as adjunctive therapy, did not show efficacy in newly diagnosed children and adolescents with IBD.