Beginning with Lev Vygotsky's long-established assertion that the play of children always involves both imaginary play and rules of behavior, this article argues for a theoretical framework that connects such play with the construction of social identities in kindergarten peer groups. It begins with a discussion of Ivy Schousboe's model of the different spheres of reality in children's play to explain symbolic group play and applies the model to the play of a group of five-year-old kindergarten soccer players. The article finds that the soccer games of kindergartners and their negotiations of play rules intrinsically involve their social identities, both those that are real and those that are imaginary.