<p>Social participation is a critical factor influencing depression in older adults. This study investigates the impact of social participation trajectories on depression risk among older Chinese adults, using data from five waves of the China Health and Retirement Longitudinal Study (CHARLS, 2011–2020). A life course perspective identified three trajectories of social participation: increasing, low-steady, and decreasing. Cox proportional hazards models revealed that, compared to the low levels of social participation, higher levels of social participation are associated with a lower risk of depression. These findings highlight the protective role of the extent of social participation to mitigate depression risk. This study advances prior research by applying the growth mixture modeling (GMM) approach to capture the temporal dynamics of social participation, offering new support for gerontological theories. Practical implications include improving community infrastructure and expanding childcare and older adult care services to support social participation to prevent depression in later life.</p>