Background: Vedolizumab (VDZ), an adhesion molecule inhibitor and infliximab (IFX), a tumor necrosis factor (TNF) blocker, are both approved as first-line induction agents in moderately to severely active ulcerative colitis (UC). However, there are no head-to-head studies comparing the relative effectiveness of the two agents. Here we provide a real-world comparison of these two agents. Methods: We conducted an ambidirectional cohort study of adult UC patients seen at our tertiary inflammatory bowel disease (IBD) center from 2012 to 2017. Each patient had moderately to severely active UC via partial Mayo score and was induced with IFX or VDZ. They were followed until assessment of clinical response. Poisson regression was used to calculate clinical response rates and rate ratios. Results: Of 59 patients who met inclusion criteria, 27 and 32 patients were induced with IFX and VDZ, respectively. Totally, 18/27 (66.7%) patients induced with IFX vs. 24/32 (78.1%) patients induced with VDZ were clinical responders. Response rates per 100 person-weeks (PW) were similar for VDZ (5.21) and IFX (5.38). The effectiveness in terms of induction of clinical response (incidence rate ratio, IRR) was not statistically significant for VDZ vs. IFX (IRR 0.97, 95% confidence interval (CI) 0.53 - 1.77). Among TNF blocker naive patients, IRR was also not statistically significant between VDZ (6.74/100 PW) and IFX (6.48/100 PW) (IRR 1.04, 95% CI 0.47 - 2.29). Among TNF blocker experienced patients, there was a higher response rate for VDZ (4.52) vs. IFX (2.29) per 100 PW, but the IRR did not reveal statistical significance (IRR 1.97, 95% CI 0.45 - 8.63) due to small sample size of TNF blocker experienced patients who received IFX. Five patients developed severe infection or adverse reaction during IFX induction requiring exclusion, whereas no VDZ patients were excluded for this reason. Conclusions: Our study revealed a higher proportion of patients who responded to VDZ vs. IFX; however when accounting for period between induction and assessment of clinical response, rates of clinical response were similar. A key difference between the two groups was the higher response rate in the VDZ group among TNF blocker experienced patients; however, a larger cohort is needed to further elaborate on this difference. VDZ held its own against IFX and this study strengthens its standing as a first-line agent among TNF blocker naive as well as TNF blocker experienced UC patients.