Research Findings: The Classroom Assessment Scoring System Toddler (CLASS-T) is one of the most commonly used measures to assess the quality of teacher-child interactions in toddler classrooms. Despite widespread use of the CLASS-T, few studies have examined the factor structure of the CLASS-T for use in Early Head Start (EHS) and subsidized child care programs serving children from low-income, ethnically and linguistically diverse backgrounds. The purpose of the present study was (a) to examine the factor structure of the CLASS-T in a sample of 106 classrooms comprised of ethnically and linguistically diverse toddlers attending EHS and subsidized child care programs; and (b) to examine the invariance of the factor structure across classrooms in which teachers spoke predominantly English or Spanish in the classroom. Findings supported the two-factor structure of the CLASS-T, which included the Emotional and Behavioral Support and Engaged Support for Learning domains. Additionally, findings provide preliminary support for the use of the two-factor structure of the CLASS-T in linguistically diverse classrooms. Practice or Policy: Overall, research findings provide evidence for the use of the CLASS-T to measure quality within toddler classrooms that serve ethnically and linguistically diverse toddlers. Future directions and implications for both policy and practice are discussed. (author abstract)