Professional identity development of play therapists is an emerging topic of research. Though there is research on theoretical orientation development, there is no research on theoretical orientation development of play therapists. This constructivist grounded theory study aimed at developing a substantive model describing the process of theoretical orientation development of play therapists. Fifteen Registered Play Therapists[TM] participated in semi-structured interviews exploring the process of developing their theoretical orientation in play therapy. A conceptual model documents the process involved in the theoretical orientation development in play therapy. The coding process in the constructivist grounded theory methodology identified five main steps: functionality of original theoretical orientation, search for a child-appropriate theory, play therapy training, application of skills, and authenticity. The findings of this study aligned with past research but also revealed new processes unique to play therapists. This study offers insight into what counselor education programs, supervisors, and the Association for Play Therapy can do to support play therapists' theoretical orientation development through earlier education and practice with child-appropriate theories to maintain the high standards of the Association for Play Therapy while maintaining within the bounds of CACREP and ACA. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]