Despite widespread concerns that misinformation is rampant on social media, little systematic and empirical research has been conducted on whether and how news consumption via social media affects people's accurate knowledge about COVID-19. Against this background, this study examines the causal effects of social media use on COVID-19 knowledge (i.e., both in the form of factual knowledge and misinformation detection) as well as the underlying mechanisms through which such effects occur. Based on original panel survey data across six weeks (W 1 N = 1,363, W 2 N = 752) in the U.S., we found that consuming news from social media fostered the perception that one need not actively seek news anymore because it would reach them anyway through their social connections (i.e., "news-finds-me" perception). This, in turn, can make one both uninformed and misinformed about COVID-19 issues. Furthermore, this mediated relationship is stronger among those who experience higher levels of information overload while on social media.