BACKGROUND/AIMS: Previous literature suggests that the response of patients with ulcerative colitis to vedolizumab may be affected by previous biologic therapy exposure. This real-world study evaluated vedolizumab treatment effectiveness in biologicnon- naive patients. METHODS: This was a multicenter, retrospective, observational chart review of records from 16 hospitals in Japan (December 1, 2018, to February 29, 2020). Included patients who had ulcerative colitis, were aged >/= 20 years, and received at least 1 dose of vedolizumab. Outcomes included clinical remission rates from weeks 2 to 54 according to prior biologic exposure status and factors associated with clinical remission up to week 54. RESULTS: A total of 370 eligible patients were included. Clinical remission rates were significantly higher in biologic-naive (n=197) than in biologic-non-naive (n=173) patients for weeks 2 to 54 of vedolizumab treatment. Higher clinical remission rates up to week 54 were significantly associated with lower disease severity (partial Mayo score </= 4, P= 0.001; albumin >/= 3.0, P= 0.019) and the duration of prior anti-tumor necrosis factor alpha (anti-TNFalpha) therapy (P= 0.026). Patients with anti-TNFalpha therapy durations of < 3 months, 3 to < 12 months, and >/= 12 months had clinical remission rates of 28.1%, 32.7%, and 60.0%, respectively (P= 0.001 across groups). CONCLUSIONS: The effectiveness of vedolizumab in biologic-non-naive patients was significantly influenced by duration of prior anti-TNFalpha therapy. (Japanese Registry of Clinical Trials: jRCT-1080225363).