in order to teach mathematics well, teachers must have a specialised knowledge of the content (silverman & thompson, 2008) and believe in effective teaching methods (philipp, 2007). research has indicated that teaching mathematics effectively may require teachers to use pedagogy that they have never experienced themselves (mcneal & simon, 2000). to address the important issue of effective mathematics instruction, professional learning groups have been explored as a means to provide teachers the support they need to continue developing professionally. this research addresses a call by johnson (2009) that professional learning groups need to be investigated further to ensure their effectiveness. a case study of one professional learning group was conducted to explore how the discussions provided the needed support for mathematics teachers in using research-based pedagogy in their classrooms. professional learning group characteristics provided by the research literature were examined in relation to this case study in order to determine how such groups could be developed in mathematics. conversations about beliefs and knowledge were also analysed, in order to provide an understanding of how the group focused on mathematics teaching and learning. narrative inquiry was used to provide in-depth descriptions of five of the teachers, chosen in order to show a range of the members within the group. through both the case study and narrative, a model was created, in order to provide a description of characteristics and dynamics needed in a professional learning group in order to support teachers in their mathematics teaching development. the potential of the model to analyse other research on mathematics professional learning groups was briefly examined. this research determined that to encourage teachers to make changes in their teaching, the professional learning group model should center on an action research type mentality with a “leader” pushing conversations toward more research-based pedagogy. furthermore, professional learning groups in mathematics need to consider the beliefs and knowledge of the group members in order for the professional development to be effective.