BACKGROUND: Small bowel capsule endoscopy is a valuable modality for evaluating small intestinal lesions in children with inflammatory bowel disease. However, its application for very early-onset inflammatory bowel disease remains insufficiently documented. This study investigated the feasibility and safety of small bowel capsule endoscopy for very early-onset inflammatory bowel disease. METHODS: A cohort of patients with very early-onset inflammatory bowel disease who underwent small bowel capsule endoscopy at under 6 years of age between January 2013 and December 2022 at 7 Japanese pediatric centers was included. Their medical records were retrospectively reviewed for actual procedures, safety, and test results. RESULTS: Eighty-two patients (21 with ulcerative colitis, 25 with Crohn's, 31 with inflammatory bowel disease-unclassified, 4 with monogenic inflammatory bowel disease, and 1 with intestinal Behcet's disease) were enrolled, and 104 small bowel capsule endoscopies (median age, 3.8 years; median body weight, 13.0 kg) were analyzed. All capsules were deployed endoscopically, mostly using delivery devices (95%). Gastrointestinal patency was assessed in 95% of procedures, most commonly using patency capsules (70%). Abnormal small bowel findings were observed in 42% of patients, with aphthae being the most common (34%), followed by ulcers (18%). No serious complications, including small intestinal retention and perforation, were reported. CONCLUSIONS: Small bowel capsule endoscopy for very early-onset inflammatory bowel disease is feasible with diagnostic utility, and it can be performed safely with appropriate evaluation using patency capsules.