Social vulnerabilities are associated with higher COVID‐19 disease morbidity and mortality. Primary forms of COVID‐19 disease prevention aside from vaccination, are health behaviors including masking, hand washing, social distancing, and staying home when one is sick. Understanding the self‐efficacy of these behaviors in vulnerable populations can inform health interventions to improve COVID‐19 disease outcomes. A repeated cross‐sectional study with three waves (Wave 1 = pilot, Wave 2,
n
= 1258, Wave 3,
n
= 477) was conducted using an online survey. This analysis only included Wave 2 and Wave 3. The study targeted Yakima County, WA, USA, an area with pronounced social, environmental, and health disparities. Measures included demographic, household, and self‐efficacy constructs. Binary logistic regression was used to determine which demographic and household factors were related to constructs of self‐efficacy. An independent
t
‐test was performed to determine if there were significant differences between population levels of self‐efficacy over time (Wave 2 vs. Wave 3). Household size, identifying as Hispanic/Latino, and measures of socioeconomic status were significantly related to various self‐efficacy beliefs about COVID‐19 disease prevention behaviors and the ability to protect oneself from COVID‐19 disease in general. Self‐efficacy increased for each measure between Wave 2 and Wave 3 (
p
< 0.001). Socially vulnerable groups continue to experience disparate health outcomes in the face of COVID‐19 disease. Future studies should examine ways to increase self‐efficacy among populations that are experiencing lower levels as self‐efficacy is a significant factor related to health outcomes.