WHAT IS KNOWN AND THE OBJECTIVE: De novo Crohn's disease (CD) is an increasingly reported diagnosis after ileal pouch anal anastomosis (IPAA). Currently, no consensus exists on the best treatment strategy. CASE SUMMARY: This report details the case of a 5-year-old child with early-onset ulcerative colitis (UC) who developed findings compatible with CD 12 months after IPAA. Thalidomide therapy led to clinical and endoscopic remission without side effects at 6 months. WHAT IS NEW AND CONCLUSION: To our knowledge, this is the first report of thalidomide for treatment of de novo CD. Thalidomide therapy could be considered in patients with de novo CD, with similar indications of CD.