The COVID-19 pandemic prompted rapid development of scarce resource allocation policies (SRAPs) in case demand for critical health services eclipsed capacity. To test whether a brief educational video could improve knowledge of how the University of California Health's SRAP would be implemented and trust in health systems to implement such policies in accordance with ethical principles during the pandemic. This randomized clinical trial used an educational video intervention embedded in a longitudinal web-based survey and was conducted between May and December 2020 and analyzed during March 2024. A total of 1971 adult participants were enrolled, of whom 939 completed follow-up; participants with matched baseline and follow-up responses were analyzed. California residents were randomized to view the intervention (n = 345) or not (n = 353) and stratified by age, sex, education, racial identity, and self-reported health care worker status. Non-California residents were allocated to the control group (n = 241). A brief (6-minute) "explainer" video that provided an overview of mechanics and ethical principles underpinning the University of California Health SRAP, subtitled in 6 languages. Self-reported survey assessment of knowledge of components of SRAP, graded as correct vs incorrect, and trust graded on a 10-point Likert scale. Anxiety about such policies was graded on a 10-point Likert scale with an a priori noninferiority margin of half of a standard deviation. Participants answered items at baseline and follow-up (approximately 10 weeks after baseline), with randomization occurring between administrations. Of 770 randomized participants with responses at both points, 566 (73.5%) were female, and the median (IQR) age was 43.5 (36-57) years. Intervention participants demonstrated improvement of 5.6 (95% CI, 4.8-6.4; P < .001) more correct knowledge items of 20 vs controls, as well as significant improvements in reported trust in fairness/consistency and honesty/transparency about SRAP implementation. There was no significant change in reported anxiety surrounding SRAP in either treatment or control groups. The trial found that a brief educational video is sufficient to explain complex ethical tenets and mechanics of SRAP and improved knowledge of such policies and trust in health systems to implement them equitably while not exacerbating anxiety about potential policy implications. This informs practice by providing a framework for educating people about the use of these policies during future situations necessitating crisis standards of care. ClinicalTrials.gov Identifier: NCT04373135.