<p>This study uses the 2016–2022 waves of the China Family Panel Studies (CFPS) to examine how care from adult children affects elderly healthcare expenditures, with a focus on the moderating role of social care services. Three key findings emerge. First, care from adult children significantly reduces medical expenses by improving health monitoring, nutrition, and health behaviors—acting as a substitute for formal healthcare. This result holds under multiple robustness checks. Second, this effect operates primarily through the promotion of healthy lifestyles, improved management of chronic diseases, and enhanced psychological outlook, thereby strengthening the overall health status of older adults. Additionally, heterogeneous effects show that the benefits of caregiving are stronger among lower- and middle-income households, families where mothers are the primary care recipients, and particularly among disabled elderly individuals—highlighting how economic vulnerability, gendered family roles, and functional health status jointly shape the dynamics and impact of intergenerational care. Third, increased access to social care services (e.g., institutional beds and community-based programs) strengthens rather than weakens the effectiveness of family caregiving, indicating a complementary relationship between formal and informal care. In areas with greater institutional capacity, formal systems help relieve routine and high-intensity tasks, enabling family members to focus on emotional support and health management. This coordination enhances the overall efficiency of eldercare and leads to greater reductions in healthcare expenditures. These findings highlight that formal and informal care function as mutually reinforcing components of an integrated care system, offering both theoretical insight and policy relevance for promoting sustainable eldercare in aging societies.</p>