Objective: Recent studies suggest that parents maintain influence as their adolescents transition into college. Advances in communication technology make frequent communication between parents and college students easy and affordable. This study examines the protective effect of parent-college student communication on student drinking behaviors, estimated peak blood alcohol concentration (eBAC), and serious negative consequences of drinking. Participants: Participants were 746 first-year, first-time, full-time students at a large university in the United States Methods: Participants completed a baseline and 14 daily Web-based surveys. Results: The amount of time spent communicating with parents on weekend days predicted the number of drinks consumed, heavy drinking, and peak eBAC, consistent with a protective within-person effect. No association between communication and serious negative consequences was observed. Conclusions: Encouraging parents to communicate with their college students, particularly on weekend days, could be a relatively simple, easily implemented protective process to reduce dangerous drinking behaviors. (Contains 2 figures and 1 table.)