OBJECTIVE: The objective of this population-based study was to determine if and to what extent there are differences in asthma self-efficacy by race/ethnicity and income, and whether health status, levels of acculturation, and health care factors may explain these differences. METHODS: We conducted a secondary data analysis of asthma self-efficacy using the 2009 and 2011-2012 California Health Interview Survey, in adults with asthma (n=7874). In order to examine if and how the effect of race/ethnicity and income on asthma self-efficacy may have been altered by health status, acculturation, and health care factors, we used staged multivariable logistic regression models. We conducted mediation analyses to evaluate which of these factors might mediate disparities in self-efficacy by race/ethnicity and income. RESULTS: 69.8% of adults reported having high asthma self-efficacy. Latinos (OR 0.66; 95% CI 0.51-0.86), African-Americans (OR 0.50; 95% CI 0.29-0.83), American Indian/Alaskan Natives (OR 0.55; 95% CI 0.31-0.98) and Asian/Pacific Islanders (OR 0.34; 95% CI 0.23-0.52) were less likely to report high self-efficacy compared to Whites. Individuals with income below the federal poverty level (OR 0.56; 95% CI 0.40-0.78) were less likely to report high self-efficacy compared to higher income individuals. The relationship between income and self-efficacy was no longer significant after further adjustment for health care factors; however, the differences in race and ethnicity persisted. Receiving an asthma management plan mediated the relationship in certain subgroups. CONCLUSIONS: Addressing modifiable health care factors may play an important role in reducing disparities in asthma self-efficacy.