The purpose of this study is to analyze how particular mathematics teacher educators (MTEs) use knowledge in their practice. Furthermore, this study also examines how they use this analysis as a tool for understanding the knowledge demands of work with preservice elementary teachers and how this knowledge is different from that required to teach K-12 students. The authors describe different forms of knowledge observed across different mathematics teacher educators’ practice and discuss how the observed knowledge forms are different from knowledge used by K-12 teachers in their practice. They argue that there needs to be more of a focus on understanding the knowledge drawn on by teacher educators as they teach content to preservice teachers.