Objective: In 2016 a private Missouri university implemented a campus-wide tobacco-free policy to change social norms and prevent tobacco use among students, staff and faculty. This study assesses impact on tobacco and policy-related perceptions and behaviors. Methods: Before the policy went into effect and again one year later, all university students, staff and faculty were invited to participate in an online survey. Missouri Assessment of College Health Behaviors survey findings supplement results for students. Results: Policy support and norms disapproving tobacco use on campus increased, and self-reported use of any tobacco decreased after the ban was enacted. Conclusions: Our results suggest that the policy led to an increase in the proportion of university community members who agree that smoking on campus is unacceptable, which contributed in turn to a decline in tobacco use on campus, consistent with our theory of effects.