In Fonagy and Target's (1996, 2000) developmental model of mentalization, play is theorized as a precursor of later mentalization and reflective function (RF); however, the relationship between play and later mentalization and RF has yet to be empirically tested. These processes are particularly important in the context of trauma, but an empirical model of the relationships among mentalization, play, and trauma is currently lacking. The aim of this longitudinal study was to examine whether children's capacity to engage in pretend play, to symbolize, and to make play narratives was associated with later RF in those children. Thirty-nine sexually abused children and 21 nonabused children (aged 3 to 8) participated in the study. The Children's Play Therapy Instrument was used to assess children's free play. Three years after the play assessment, children's RF was assessed using the Child Attachment Interview, coded with the Child and Adolescent Reflective Functioning Scale. Pretend play completion was associated with later other-understanding. Play was also found to mediate the relationship between sexual abuse and children's later mentalization regarding others. These findings are consistent with Fonagy and Target's emphasis on the role of pretend play in the development of a nuanced sense of the qualities of the mind and reality. In sum, the findings lend support to Fonagy and Target's account of playing with reality, and the development of mentalization suggests that it may be more than "fiction." Furthermore, these results suggest that children's ability to create meaningful and coherent play sequences after sexual abuse is associated with the development of a better understanding of their relationships with others. Clinical implications and future directions are discussed.