The results of this study establish the validity of the Student Interest Scale and Student Engagement Scale, as well as associations among teacher communication behaviors, student interest, and engagement. Confirmatory factor analysis indicates that the factor structures of the measures are stable, reliable, and valid. The results indicate positive relationships among teacher immediacy and clarity, and student emotional and cognitive interest and engagement, providing initial evidence for construct validity. Theoretical and pedagogical implications are discussed. (Contains 3 tables.)