The positive effects of participation in social activities have been studied in various fields, including political science (in relation to democracy and trust), gerontology, and sociology (for its effects on physical and mental health). Against a background of rapid population ageing, the study of social integration among the elderly is of particular relevance within the framework of active ageing. Yet, whether the relationship between kin and non-kin social activities is characterized by cumulation or competition remains under-explored. In particular, grandparenting has taken a central role for the elderly due to unprecedented overlap between grandparents' and their grandchildren's lives. Grandparenting may stimulate social participation or it may impose time and energy constraints on it. This study aims to assess the effect on the participation in social activities among the elderly of providing childcare on a regular basis. Using an instrumental variable approach on data from the Survey of Health, Ageing and Retirement in Europe, we find that regular provision of childcare has a significant negative effect on the number of activities in which grandmothers participate. When considering the activities separately by type, we find a negative effect on engagement in educational or training courses for both grandfathers and grandmothers, while a negative effect on volunteering and participating in political or community-related organization is additionally found only for grandmothers. These results contribute to the debate on active ageing