Youth and young adults (YYA) have been uniquely affected by COVID-19. Behavioral models have not yet been applied to understand YYA’s preventive behavior, though the Information–Motivation–Behavior (IMB) model may be appropriate. We used data from a national, diverse survey of COVID-19 effects and prevention behaviors in YYA ages 14–24 (n = 1026) and conducted an exploratory factor analysis and bivariate linear regressions to assess the association between demographics and IMB measures. Significant differences by sexual identity were identified, with bisexual/pansexual, gay/lesbian, and queer populations reporting significantly lower prevention stigma, in comparison to their straight respondents. Non-binary respondents (vs. women/girls) and transgender and gender diverse individuals (vs. cisgender) had significantly higher intentions to social distance. Racial/ethnicity differences were also found in lower prevention efficacy beliefs (Latinx and multiracial vs. white), and lower motivation norms (Black and Latinx vs. white). Our findings about critical disparities in IMB measures provide recommendations for future prevention research, practice, and policy development in response to the pandemic, particularly related to highly marginalized communities.