Background <p>This study examines how adolescents’ media message perceptions during a pandemic were associated with preventive health behaviors (PHBs; e.g., mask wearing).</p> Methods <p>A U.S. sample of 154 adolescents aged 13–17 were asked to complete surveys every two weeks over 6 months (May 2021–December 2022). Multilevel models tested associations of five media message perceptions (feeling informed, feeling connected, positive perceptions of government leadership, negative impressions of public health measures, and feeling afraid) with PHBs, adjusting for covariates.</p> Results <p>Boys, vaccinated adolescents, higher-SES youth, and those living in more Republican counties showed fewer PHBs. Feeling informed and afraid in response to COVID-19 media messages were associated with more PHBs. Negative impressions of public health measures were linked to fewer PHBs, particularly among older adolescents. The association between feeling afraid and PHBs was stronger in older adolescents. Feeling informed was linked to more PHBs in non-Asian adolescents, while feeling connected was linked to more PHBs in non-White adolescents.</p> Conclusion <p>Adolescents’ PHBs are shaped by how they perceive and emotionally respond to media messages. Messages that emphasize clear information, establish the credibility of public health measures, cultivate appropriate risk perceptions, and consider demographic differences may increase adolescents’ PHBs and preparedness.</p> Impact <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Adolescents’ perceptions of media messages and demographic characteristics may relate to their preventive health behaviors (PHBs) such as mask wearing over time.</p> </ItemContent> <ItemContent> <p>Using longitudinal data from 154 U.S. adolescents across six months and 13 surveys, this study extends prior cross-sectional work during the pandemic.</p> </ItemContent> <ItemContent> <p>Findings show PHBs declined but media message perceptions remained influential. Feeling informed or afraid by media messages predicted greater PHBs, while negative impressions of media messages predicted lower PHBs.</p> </ItemContent> <ItemContent> <p>Age and racial/ethnic differences emerged, underscoring the need for tailored communication for adolescents.</p> </ItemContent> <ItemContent> <p>Results can inform health campaigns to better support adolescents’ protections during future health crises.</p> </ItemContent> </UnorderedList></p>