Background <p>Misinformation has emerged as a major concern for public health during the COVID-19 pandemic. Our study conceptualizes trust in doctors and social support through the lens of social capital theory and investigates their role in public endorsement of COVID-19-related misinformation.</p> Methods <p>Using data from a nationally representative survey (<i>N</i> = 6,515), a series of logistic regression models were used to estimate relationships between misinformation endorsement and trust in doctors and social support from interpersonal and communal sources. Moderation analyses explored differences in these relationships among non-Hispanic White, non-Hispanic Black, and Hispanic respondents.</p> Results <p>In the full sample analysis, trust in doctors and social support from both sources were negatively associated with misinformation endorsement. This pattern did not consistently hold across the three subgroups in moderation analyses. Trust in doctors was negatively associated with misinformation endorsement in most cases, whereas social support exhibited varied associations depending on its source and respondents’ race and ethnicity.</p> Conclusions <p>These findings confirm that trust in doctors is an important protective factor against COVID-19 misinformation. The role of social support, however, is more nuanced and warrants continued research that considers both support sources and the racial and ethnic background of the communities involved.</p>