<p>With China’s rapidly aging population, the mental health of older adults has become a growing concern. Although existing research suggests that individuals and their children’s characteristics have a significant impact on the mental health of elderly parents, less is known about the impact of adult children’s educational mobility on elderly parents’ mental health. Drawing on data from the 2016, 2018, and 2020 waves of the China Longitudinal Aging Social Survey (CLASS), this study examines the effects of intergenerational educational mobility on the mental health of older adults in both single-child and multi-child families, while also exploring the moderating role of co-residence using the Diagonal Reference Model. The results indicate that children’s educational attainment influences their parents’ mental health more than their parents’ own education, especially in multi-child families. Additionally, the effect of children’s educational mobility is weaker compared to their educational attainment. Co-residence with children significantly moderates the relationship between educational mobility and mental health, but this effect is observed only in single-child families. Our research contributes to the literature on social mobility by advancing the understanding of these dynamics in the context of a transforming China, while also enhancing the analysis of heterogeneity across different family structures and living arrangements. The findings support Blau’s argument on the primacy of position effects over mobility, offering valuable insights into the mental health of older adults in China, and highlighting important implications for eldercare policies.</p>