Most counselors agree that the therapeutic relationship is essential in counseling. However, the current evidence-based treatment movement has resulted in a focus on treatment protocols and techniques in outcome research. Researchers have called for the inclusion of relationship variables in future outcome research. Child-centered play therapy (CCPT) is an empirically-supported, developmentally responsive intervention for children that emphasizes building a therapeutic relationship based on the philosophy of person-centered theory. Exploring the impact of the relationship on CCPT outcomes would be beneficial, but no current quantitative measure exists for obtaining the child’s view of the therapeutic relationship. The purpose of this study was to create a developmentally appropriate instrument to measure children’s perceptions of the therapeutic relationship. Established instrument development procedures were followed to create the Relationship Inventory for Children (RIC), a 15-item instrument for use in outcome research that measures the child’s perspective of the therapeutic relationship. Participants were 33 child experts who participated in interviews and preliminary testing of the instrument as well as 100 children whose scores on the 31-item pilot instrument were submitted to exploratory factor analysis (EFA). Children (62% male) ranged in age from 6 to 9 years (M = 6.92) and 53% identified as Caucasian, 14% as Hispanic, 14% as African American, 2% as Asian American, 0.8% as Native American, 8% as Multiracial, and 9% unreported. The EFA resulted in three factors: Positive Regard, Unconditional Acceptance, and Empathy. Implications for further development of the RIC, for use of the RIC in research, and for application of the RIC to person-centered theory are discussed.