The present study investigated the measurement properties of the Classroom Assessment Scoring System (CLASS) Toddler using data from 276 classrooms and 375 teachers in Dutch early childhood education and care provisions. First, confirmatory factor analyses based on the CLASS Toddler indicators confirmed the eight-dimension structure of the instrument. Second, a three-domain structure, involving Emotional Support, Behavioral Support and Engaged Support for Learning, fitted the data better than the commonly found two-domain structure that combines Emotional and Behavioral Support into one domain. Third, using Item Response Theory (IRT), we found good item difficulty and discrimination parameters of the CLASS Toddler indicators. Finally, significant associations were found between the CLASS Toddler domains and children-to-staff ratio, teachers' work experience and provided play and literacy activities, supporting the criterion validity of the instrument. Taken together, these results showed adequate measurement quality of the CLASS Toddler. Implications for practice are discussed. (author abstract)