The purpose of this research was to study the implementation of a professional learning community comprised of one group of third-grade teachers in a Florida elementary school where the emphasis was on research-based practices in the teaching of mathematics. Investigated were the growth of teachers‟ content knowledge in mathematics, specifically in the areas of multiplication and division, and the effects of their professional learning within their classrooms. Specifically this study looked at whether or not the participation of a group of third grade teachers in a professional learning community PLC improved the mathematical content knowledge of the participants of the study. This research design called for the research to be conducted in three phases. In Phase I, the researcher interviewed all participants using a researcher-designed interview guide. A researcher-adapted survey, based upon previously released items Ball (2008) was administered as a pre-test of mathematical content knowledge,. In Phase II of the study, the researcher documented the activities that occurred within a 10-week long professional learning community (PLC) of third-grade teachers. In Phase III of the research, a post-study interview was conducted with each of the participants by an independent observer to elicit participants‟ perceptions and observations based on their participation in the PLC. A post-test of content knowledge was also administered to the participants. Several themes were identified in the research study. These themes led to recommendations for practice and future research. Themes were related to the lack of iv mathematical understanding experienced by some teachers and the lack of professional development specifically related to mathematics, the value of the professional learning community, and the benefits of sharing current research and best practices. During this study, the participants were able to read and share examples of research-based best practices in mathematics, and participants then used this new information and additional mathematics content knowledge in their classrooms in teaching their students.