Research Findings: This study investigated the relationship between features of the classroom environment and misalignment between teacher and observer ratings of preschoolers' classroom engagement and the extent to which years of teaching experience moderated this relationship. In a sample of 116 preschoolers and 21 teachers in 29 classrooms, classroom engagement was assessed using teacher report and independent direct observation. Classroom-level predictors included severity of challenging behaviors, child:adult ratio, and the percentage of students from economically disadvantaged backgrounds. Lower misalignment was noted on ratings of negative engagement than positive engagement. Multilevel regression analyses revealed that misalignment was largely independent of variation in classroom factors, except for a consistent interaction between years of teaching experience and child:adult ratio. Specifically, observers' ratings were less misaligned with novice teachers' ratings than veterans' in classrooms with a high child:adult ratio, whereas the opposite trend was found in classrooms with low child:adult ratios. Practice or Policy: Findings are discussed in light of current best practice calling for a multidisciplinary approach when conducting assessments on young children, despite little guidance on how to handle misalignment between raters when determining service eligibility and developing effective interventions. (author abstract)