Background: Supported decision-making may increase self-determination among adults with intellectual disabilities by encouraging and empowering them to make decisions about their lives to the greatest extent possible. The aim of this study was to explore the perceptions and experiences of mothers of adults with intellectual disabilities in Ireland of providing support in decision-making. Methods: Semi-structured interviews were conducted with seven mothers who had an adult son or daughter with an intellectual disability; transcripts were thematically analysed. Findings: Three main themes were identified: support (family, services and routine), decision-making (importance, ability and Capacity Act) and challenges (conflict, time, complex and enduring support needs and vulnerability). Conclusions: The findings indicate that although mothers were supportive of the rights of their adult children with intellectual disabilities to make their own decisions, they were often hesitant to fully relinquish control in an effort to protect and guide them.