Objective: To examine whether policies prohibiting smoking on college campuses contribute to greater decreases in smoking. Participants: This study compares smoking prevalence and perceptions of prevalence pre/post a smoking ban enacted in 2015 by using repeated cross-sectional surveys administered at a university in 2011 (n = 1.548), 2013 (n = 3.657), 2015 (n = 3.456), 2016 (n = 2.575), and 2018 (n = 4.600). Methods: Regression models evaluated trends in prevalence with a spline term to evaluate differences after the smoking ban. Results: Before the ban, the prevalence of any past 30-day smoking decreased each survey period (AOR = 0.89, 95%CI: 0.85, 0.97); after the ban, a significantly greater decrease was observed (AOR = 0.78, 95%CI: 0.74, 0.83). Similar patterns were observed specifically for cigarette use as well as students' perceptions of the proportion of the student body who use tobacco and nicotine products. Stratified analysis identified that pre/post declines were largest in the youngest age category. Conclusions: Results support the effectiveness of campus-based antismoking policies.