This study sheds light on sibling mediation of young children's media use, focusing on older brothers and sisters as significant mediators in imparting preferences, skills, and norms of media use in early childhood. The sample included 20 families with two or three children, one of whom was four to seven years of age and had at least one older sibling. In each family, in-depth interviews were conducted with the mothers, younger children, and with the older siblings. The findings indicated that older siblings served as playmates, digital mentors, parental proxies, and shields. These roles were crucial in their younger siblings' media experiences, and much more significant than were the mediating roles of the parents, especially regarding the use of digital media.