Abstract: Background Family members of parents with intellectual disabilities (ID) are viewed as their main source of support. However, the existence of family involvement itself does not guarantee that such support will be beneficial. Aims This study draws on the perspectives of social workers to describe and evaluate involvement by Israeli family members (grandparents) in the lives of their adult children with ID (parents with ID) who themselves have become parents. Method A thematic analysis was conducted in 21 semi-structured interviews with social workers serving parents with ID through social service departments. Results From the social workers’ perspectives, grandparent attitudes regarding their adult children with ID procreating and parenting ranged from strong resistance to active encouragement. Two sub-themes of grandparent involvement were identified from the social workers’ perspectives: the critical role of grandparent support, and the complex relationships between grandparents and the parents with ID. Two further and interrelated subthemes emerged on the role of social worker engagement with grandparents. Conclusions Professionals should be aware that grandparent involvement can either support or undermine the parenting function of parents with ID. Social service professionals need to promote family involvement that empowers parents with ID by supporting their needs and roles, but without supplanting their primary parenting activities.