In middle childhood, many girls go through a curious metamorphosis, in which their earlier embrace of all-things-feminine appears to transform into an identity as a tomboy. We believe this striking shift, observed in girls but not boys, signifies a critical development in children’s socio-cognitive functioning, with implications for their understanding of gender as it relates to their identity and their social relationships. In this article, we review the evidence for this identity shift and present a theoretical account that integrates ideas from social cognition and social development. We argue that this identity shift involves the emergence of public regard and status awareness, with concurrent increases in the complexity with which knowledge associated with gender categories is represented in the mind. We then posit that these changes have important implications for the developmental trajectory of implicit and explicit gender attitudes and stereotypes, and we present a set of predictions generated by our theoretical analysis.