Purpose: Clinician–client relationships may influence treatment success in speech-language pathology, but there are no established tools for measuring these relationships. This study describes the development and application of a set of scales for assessing clinician–client relationships in children’s speech-language treatment. Method: Twenty-two triads of participants completed a longitudinal study. Each triad had 1 school-age child enrolled in speech-language treatment, 1 caregiver, and 1 speech-language pathologist (SLP). The clinician–client relationship scales were administered to all 3 types of participants at study onset and again 2 weeks later. Treatment progress measures were collected 4 months later. Analyses established the reliability and validity of the clinician–client relationship scales. Results: Adequate internal consistency reliability and test–retest reliability were established for all 3 versions of the scale (child, caregiver, and SLP). Convergent validity was moderate between SLPs and children but lower when caregivers were included. Predictive validity analyses established significant relationships between caregiver and SLP ratings of the clinician–client relationship and future treatment progress. Conclusions: This exploratory study established the viability of the clinician–client relationship scales for further development and application. The importance of establishing and utilizing measures of the clinician– client relationship in speech-language pathology is discussed.