BACKGROUND: There is little consensus as to the effects of insurance expansion on emergency department (ED) utilization for mental health purposes. We aimed to study the race specific association between the dependent coverage provision of the Affordable Care Act (ACA) and changes in young adults' usage of emergency department services for psychiatric diagnoses. METHODS:We utilized a Quasi-Experimental analysis of ED use in California from 2009–2011 for behavioral health diagnoses of individuals aged 19 to 31 years. Analysis used a difference-in-differences approach comparing those targeted by the ACA dependent provision (19–25 years) and those who were not (27 to 31 years), evaluating changes in ED visit rates per 1000 in California. Primary outcomes measured included the quarterly ED visit rates with any psychiatric diagnosis. Subgroups were analyzed for differences based on race and gender. RESULTS:The ACA dependent provision was associated with 0.05 per 1000 people fewer psychiatric ED visits among the treatment group (19–25 years) compared to the control group (27–31 years). Hispanics and Asian/Pacific Islanders were the only racial subgroups who did not see this significant reduction and were the only racial subgroups that did not see significant gains in the proportion of psychiatric ED visits covered by private insurance. CONCLUSION:The ACA dependent provision was associated with a modest reduction in the growth rate of ED use for psychiatric reasons, however, racial disparities in the effect of this provision exist for patients of Hispanic and Asian/Pacific Islander racial groups.