The COVID-19 pandemic has significantly impacted individuals' financial well-being and mental health. This study investigates the relationship between income loss and mental health outcomes during the pandemic, as well as the heterogeneity in this relationship by race/ethnicity and co-ethnic density in the metropolitan area. Using nationally representative Household Pulse Survey data, this study finds that income loss is associated with a heightened risk of depression and anxiety, even after controlling for individual and metropolitan-level characteristics. Co-ethnic density in metropolitan areas worsens the effects of income loss on depression and anxiety for Hispanics and non-Hispanic Blacks while residing in a metropolitan area with more Whites cushions the impact of income loss on depression and anxiety for non-Hispanic Whites. Overall, the study underscores the importance of considering the intersection of race/ethnicity and metropolitan-level co-ethnic density in exploring the influence of economic stressors on mental health.