Abstract Background Little is known about the association between catastrophic health expenditure (CHE) and mental health in elderly population and its potential moderators. This study examined the relationship between CHE and depressive symptoms in Chinese older persons and its difference between groups of different income level and social activity engagement. Methods We employed data from the 4 waves (2011, 2013, 2015, and 2018, N = 15,406) of the China Health and Retirement Longitudinal Study (CHARLS). A linear mixed model was used to examine the association between depressive symptoms and CHE, and interaction terms were involved in the model to examine the moderating role of social activity and income levels. Results Significant correlations have been shown between CHE and depressive symptoms(coefficient = 0.363, P