Background <p>While cross-sectional studies have established that social support and media exposure are associated with PTSD symptoms and Posttraumatic Growth (PTG), the longitudinal dynamics of these relationships in the context of digital-era disasters remain underexplored. In particular, the psychological impact of short video exposure about the floods during disasters is not well understood. This study seeks to elucidate the predictive roles of social support and short video exposure during the 2021 Henan floods on the initial levels and changes of PTSD symptoms and PTG six months post-disaster.</p> Methods <p>We conducted the study from July 20, 2021, to January 30, 2022, involving individuals affected by the disaster. A total of 279 disaster victims completed self-reported PTSD symptoms and PTG assessments at three time points (0-, 3-, and 6-months post-disaster). Utilizing a latent growth curve model, we investigated the influence of social support and short video exposure during the disaster on the initial levels and changes in PTSD symptoms and PTG.</p> Results <p>Findings indicated no significant relationship between social support and PTSD symptoms. However, social support during the disaster exhibited a positive association with the initial levels of PTG, predicting lower rates of change in PTG over time. Participants with more frequent flood-related short video exposure during the disaster reported higher initial levels of PTSD symptoms, followed by lower rates of change over time. Furthermore, short video exposure positively affected the initial levels of PTG but had no impact on changes in PTG.</p> Conclusions <p>This study provides preliminary evidence of the distinct roles of social support and short video exposure in relation to PTSD symptoms and PTG trajectories following a disaster, which suggests that longitudinal approaches are important for understanding the evolving impact of both social and media-related factors.</p>