For people experiencing mental health problems, timely access to high-quality healthcare is imperative for improving outcomes. However, limited availability of services, high out-of-pocket costs, insufficient health literacy and stigmatizing attitudes may mean people do not receive the necessary treatment. We analyze Australian longitudinal data to document the extent and predictors of horizontal inequity in mental healthcare use among people with a newly developed mild or moderate mental disorder. Importantly, we compare people with similar health, residing in the same area, thus controlling for differences in healthcare needs and availability of services. Results suggest that mental healthcare use is not significantly associated with household income or financial hardship. In contrast, we find significant inequities by educational attainment, with university graduates around 50% more likely to receive mental healthcare than high-school dropouts. These findings are robust across subsamples and alternative modeling approaches, including panel data models with individual fixed-effects. Additional explorations of the education gradient suggest a potential pathway through mental health-specific knowledge and attitudes.