This article examines how two new teachers, with varied content knowledge and preparation as teachers in mathematics education, improved their use of whole-class discourse in their mathematics classes with a mentor's assistance. Discourse has long been shown to be influential in supporting students' learning of mathematics, but the implementation of these practices can be a struggle for new teachers. To the initial surprise of both teachers, the observational data did not coincide with the perceptions that the teachers had of their practice. However, with structured and frequent support from a mentor, along with observational data, there were noticeable improvements in both teachers' ability to facilitate mathematical discourse. By the end of the term, the teachers included more students in discussions, asked more questions that probed for understanding, and reduced the amount of time spent delivering instruction. The strengthening of students' understanding of mathematics through communication is well established (Gose, 2009; Pugalee, 2001; Way, 2008) and is clearly emphasized in the National Council of Teachers of Mathematics' (2000) "Principles and Standards for School Mathematics." However, teachers' perceptions toward their capability to facilitate whole-class discourse, as well as their desired strategies in facilitating such discourse, can affect the implementation and effectiveness of researched-based practices within the classroom. This is especially true for 1st- and 2nd-year teachers. This article uses Piccolo, Harbaugh, Carter, Capraro, and Capraro's (2008) definition of mathematical discourse, as an "interactive and sustained discourse of a dialogic nature between teachers and students aligned to the content of the lesson that addresses specific student learning issues" (p. 378). (Contains 4 figures.)