Vedolizumab is an immunosuppressive drug that acts locally on the gastrointestinal tract, is mainly used for the treatment of inflammatory bowel disease, and has been reported to be effective against gastrointestinal acute graft-versus-host disease (GI-aGVHD) in adults. However, there is insufficient evidence for pediatric GI-aGVHD. We used vedolizumab in three cases of GI-aGVHD aged 1.5-4.4 years. It was significantly effective in two cases and all cases had no serious side effects. Vedolizumab might be effective and safe for pediatric GI-aGVHD refractory to other treatments. Future study awaits.