Interprofessional practice is a burgeoning movement in the field of health care. In recognition that no single profession can address the complex needs of many of today's young children, it is critical for play therapists to understand and possess interprofessional collaborative practice competencies. In this article, the specific interprofessional competency domain of knowledge of roles and responsibilities is examined as an essential precondition to effective collaboration between registered play therapists, occupational therapists, physical therapists, and speech-language pathologists working together in early-childhood settings. Fictional case examples illustrate how registered play therapists can actively collaborate with early-childhood therapists from other health-care disciplines to mutually learn from and inform one another. Implications for this mutual reciprocity have potential to improve collaboration between and across therapists within an interprofessional team.