Although emerging adults play a role in the spread of COVID-19, they are less likely to develop severe symptoms after infection. Emerging adults’ relatively high use of social media as a source of information raises concerns regarding COVID-19 related behavioral compliance (i.e., physical distancing) in this age group. The current study investigated physical distancing in emerging adults in comparison to adults and looked at the role of using social media for COVID-19 news and information in this regard. In addition, this study explored the relation between physical distancing and different social media platforms and sources.Secondary data of a large-scale longitudinal national survey (N = 123,848, 34.% male) between April and November 2020 were used. Participants indicated, ranging from one to eight waves, how often they were successful in keeping 1.5 meters distance on a 7-point Likert scale. Participants between 18 and 24 years old were considered young adults and participants older than 24 were identified as adults. Also, a dummy variable was created to indicate per wave whether participants used social media for COVID-19 news and information. A subset received follow-up questions asking participants to indicate which platforms they have used and what sources of news and information they had seen on social media. All preregistered hypotheses were tested with Linear Mixed-Effects Models and Random Intercept Cross-Lagged Panel Models.Emerging adults reported less physical distancing behaviors than adults (b = -.08, t(86213.83) = -26.79, p < .001). Also, emerging adults were more likely to use social media for COVID-19 news and information (b = 2.48, SE = .11, Wald = 23.66, p = <.001), which mediated the association with physical distancing, but only to a small extend (indirect effect b = -0.03, 95% CI = [-0.04; -0.02]). Opposed to our hypothesis, the longitudinal Random Intercept Cross-Lagged Panel Model showed no evidence that physical distancing was predicted by social media use of the previous wave. However, we did find evidence that using social media affected subsequent physical distancing behavior. Moreover, additional analyses showed that most social media platforms (i.e., YouTube, Facebook, and Instagram) and interpersonal communication showed negative associations with physical distancing while others platforms (i.e. LinkedIn and Twitter) and Governmental messages showed no or small positive associations with physical distancing.In conclusion, we should be vigilant for physical distancing of emerging adults, but this study gave no reason to worry about the role of social media for COVID-19 news and information. However, as some social media platforms and sources showed negative associations, future studies should more carefully look into these factors to better understand the associations between social media use for news and information, and behavioral interventions in times of crisis.