This study examined how evidence of students' mathematical understanding was influenced by elementary schoolteachers' enactment of instructional practices emphasized during a mathematics professional development program. Videos and field notes were collected during lessons for two teachers from the program and two matched comparison teachers. Lessons were observed when teachers espoused that their instruction aligned with the instructional practices emphasized during professional development. Inductive qualitative analyses indicated that the level of mathematical task and level of teacher direction influenced students work. More specifically, students in participants' classrooms were more likely to utilize resources (e.g., manipulatives and technology) to create mathematical representations and were able to explain mathematical concepts more clearly than students in the comparison classrooms. Implications for future studies and the design of professional development are also shared.