Background: College campuses have policies restricting smoking/vaping on campus. Previous studies involving mostly European-American students showed smoking prevalence declines following implementation of such policies. Objective: To evaluate a social media campaign promotive of stronger campus support for an existing campus no-smoking/no-vaping policy where most ([approximately]75%) of the undergraduates were non-European-American. A demographically comparable university served as a no-intervention control. Participants: Target was 200 random intercept surveys at each university during fall 2016, spring 2017. Of 800 respondents, 681 were undergraduates. Methods: Baseline and post-intervention surveys assessed awareness of and support for campus-wide smoke-free/vape-free policies. Staged smoke-free/vape-free policy violations assessed students' propensity to intervene in support of the policy. Results: Respondent support for the no-smoking/no-vaping policy did not change. Conclusions: The social media campaign and Policy Ambassadors program did not increase support for the campus no-smoking/no-vaping policy. Most ([approximately]90%) respondents agreed that the campus no-smoking/no-vaping policy was important for public health.