Recent work in developmental psychology and primatology indicates that human infants are distinguished from other primates by the end of the 1st year by their awareness that others have subjective states like their own. This early appearing awareness of the subjectivity of others forms the basis for the subsequent negotiation and elaboration of “we-ness,” that is, of shared orientations toward the world that allow the child to enter into collaborative relations with others. It is argued that this gradual working out of collaborative strategies for the elaboration of shared meanings is a principal function of joint pretend play in early childhood, and this is one of the critical developmental functions addressed in psychodynamic play therapy. Developmental theory and research contributing to this perspective is integrated with excerpts from children's joint pretend play and from play therapy case material to illustrate the precarious and improvisational nature of the negotiation of shared meaning.