Objective: To examine the influence of dynamic and trending descriptive norms on increasing physical activity and decreasing the sedentary behaviors of university students while on campus. Participants: One-hundred fifty-six university students from a Canadian university completed this study. Methods: Participants were randomly assigned to receive one of four online messages containing normative information about the on-campus behavior of university students. On-campus physical activity and sedentary behavior were measured pre- and post-message. Results: The results revealed that students exposed to the trending norm reported a greater decrease in sedentary behavior than students in the control condition, p = 0.007. Conclusion: Results provide preliminary experimental evidence that trending norm messages may serve to decrease the sedentary behavior of students while on campus.