Using 7-wave longitudinal data spanning 18 years, this paper explores the impact of grandparenting on rural older adults' physical health and psychological well-being. Moderate or intensive care, grandparenting regardless of whether living with adult children or not, and transitioning to grandparenting significantly increase older adults' (instrumental) activities of daily living, while never grandparenting and transitioning to the state of not grandparenting significantly decrease their (instrumental) activities of daily living. Intensive care, grandparenting and living with adult children, and persistent care positively affect their self-rated health, while never grandparenting negatively affects their self-rated health. Older adults who have persistently/never cared for grandchildren are more/less satisfied with their lives. Moderate and intensive grandparenting and grandparenting regardless of whether living with adult children or not significantly reduce older adults' depression, while never grandparenting and transitioning to the state of not grandparenting significantly increase the number of depressive symptoms. The results suggest that moderate grandparenting benefits older adults' physical health and psychological well-being. This might result from the harmonious interaction between their role of ageing parents and their "parent" role in intergenerational child care.