This study examines the role of teacher knowledge about reading fluency in students' fluency growth. Specifically, the effects of teacher knowledge on fluency with nonsense word reading and oral passage reading were examined. Students' vocabulary was also considered as a predictor of fluency development. Results demonstrated that teacher knowledge about reading fluency is a significant predictor of first-grade students' decoding growth and second-grade students' oral reading fluency growth. Effects on third-grade students' reading growth are less pronounced. Implications for future research and professional development practice are discussed. (Contains 10 tables and 3 figures.)