Vedolizumab (Entyvio™) is a humanized monoclonal antibody α4β7 integrin-receptor antagonist indicated for the treatment of adult patients with moderately to severely active ulcerative colitis or Crohn's disease. This article reviews the pharmacological properties of intravenous infusions of vedolizumab and its clinical efficacy in adult patients with these diseases. In phase III clinical trials, patients with ulcerative colitis had significantly higher rates of clinical response and clinical remission when treated with vedolizumab than when receiving placebo at both 6 and 52 weeks. However, outcomes with vedolizumab in patients with Crohn's disease were mixed. In a study that evaluated both clinical remission rate and CDAI-100 response rate as primary endpoints, only the clinical remission rate at 6 weeks was significantly higher with vedolizumab than placebo. In another trial, there was no significant between-group difference in the clinical remission rate in TNF-antagonist failure patients at 6 weeks (primary endpoint), although there was a significant difference at 10 weeks. In the Crohn's disease study that included maintenance treatment, vedolizumab was significantly more effective at 52 weeks than placebo in both endpoints (clinical remission was the only primary endpoint in the maintenance study). Vedolizumab was generally well tolerated in these trials. As vedolizumab is a specific α4β7 integrin antagonist, with gut-specific effects, it is unlikely to be associated with the development of progressive multifocal leukoencephalopathy, a risk observed with the less selective α4β7/α4β1 integrin antagonist natalizumab. Vedolizumab is a useful addition to the treatment options available for patients with moderately to severely active ulcerative colitis and Crohn's disease.