Communication is certainly not a new notion from the socioconstructivists' point of view, and expert teachers already recognize the importance of language as an essential tool in the dynamic process of teaching mathematics. However, dramatic differences exist in early childhood teachers' personal understandings and practices in mathematics education. Through a qualitative case study, this article explores an experienced kindergarten teacher's conception and practice of effective mathematics instruction in promoting children's communication. Data were collected through classroom observations, semistructured interviews, and classroom documents. The findings reveal that the teacher's conception of the use of communication derives from her own beliefs and teaching experience about how to develop children's mathematical thinking. The constraints of the public school system also challenge the teacher's effective mathematics instruction to engage children in rich communication. From these findings, implications are discussed for teacher educators and early childhood teachers. (Contains 1 note.)