Vedolizumab is a humanized monoclonal antibody that binds to the human a4β7 integrin and is approved for use in inflammatory bowel diseases. We describe a patient with severe, refractory erosive gingivostomatitis, which appeared a few days after the first dose of vedolizumab and resolved after discontinuation of the drug. We believe the gingivostomatitis to be a direct side effect of vedolizumab, rather than an extraintestinal manifestation of the underlying inflammatory bowel diseases. The clinicians need to be aware of this adverse event, which could be mistakenly considered as an extraintestinal manifestation of inflammatory bowel diseases.