Objective: The start of university is a critical period for health risk behavior (i.e. eating, physical activity, alcohol use) which can be influenced by expectations and by environmental factors such as living arrangement, health behaviors of close social ties (i.e. parents, partners, peers), and time spent with peers. We investigated associations between environmental factors and current/expected health behaviors of German freshmen during the COVID-19 pandemic. Method: A cross-sectional survey design was used. A total of N = 208 students (82.7% female; M age = 20.90, SD = 4.10) completed an online questionnaire assessing health behaviors and environmental factors at the beginning of their first semester. Results: Current and expected physical activity was associated to that of all social ties, current and expected alcohol use to partner's and peers' alcohol use, while current and expected eating was only associated to peers' eating. The relationship between partner's or peers' and participant's alcohol use was moderated by coresidence, with a greater probability of engaging in these behaviors observed in case of coresidence. Perceived peer encouragement for alcohol consumption moderated the relationship between peer alcohol use and the number of drinks consumed by participants per month. Participants who spend more time with peers were more likely to consume higher amounts of alcohol. No differences were found regarding present and expected behaviors of participants who moved out of their parents' home and those who did not. Conclusion: Partners and peers significantly influence students' health behaviors, particularly alcohol use. Interventions to prevent health risk behaviors among freshmen should therefore address these social ties' influence.