Research on children’s friendship in culturally diverse contexts has shown that children are more likely to choose friends from their own ethnic or racial group than others. This article examines this tendency from the perspective of 10- to 12-year-old girls attending ethnically mixed primary schools in Dublin, Ireland. It argues that both the emotional challenges involved in encounters across divides and the dynamics of all children’s friendships have a significant role to play in the manner in which boundaries are drawn.