Reliable information regarding interaction quality in preschools is essential because children's preschool experiences predict educational success. The Individualized Classroom Assessment Scoring System (inCLASS) is a new tool to assess interaction quality developed in the United States. Research on the validation of the factorial structure of the inCLASS--with the factors teacher interactions (comprising positive engagement, teacher communication), peer interactions (peer sociability, peer communication, peer assertiveness), task orientation (task engagement, self-reliance), and conflict interactions (behaviour control, teacher conflict, peer conflict)--is limited and inconsistent. This study aims to extend knowledge on the factorial validity of the inCLASS in Austrian preschools. The sample consists of 261 children (M = 49.54 months of age) from 81 preschool classes in Tyrol, Austria. Initial confirmatory factor analysis indicated negative residual variances and standardised factor loadings >1 for teacher communication and behaviour control. After modifications such as setting error residuals for teacher communication and behaviour control to zero and allowing the residuals of positive teacher engagement and peer sociability to covary the model fit was acceptable to good. The findings suggest a revision of the operationalisation of conflictual interactions and a consideration of attachment theory to explain the relationship between teacher interactions and peer interactions.