This paper discusses findings of a formal investigation into the impact of specialized courses on the development of pedagogical content knowledge of teacher candidates pursuing certification to teach mathematics in secondary schools. This study is two-phased, with phase I beginning in the final year of participants’ teacher preparation program and phase II during the first year of teaching with a subset of phase I participants. The study investigates the development of beginning secondary mathematics teachers’ pedagogical content knowledge (PCK) about teaching and learning mathematics over this two-year period. Data were compiled from multiple sources: a researcher created PCK inventory, interviews, classroom observations, and an exit survey. Each source provided information for understanding how beginning secondary mathematics teachers developed their PCK and insight into participants’ perceptions of their development. Findings from this study indicate that PCK developed through its explicit integration in the specialized courses. Participants were given assignments and opportunities to connect their Content Knowledge (CK) and Pedagogical Knowledge (PK) and begin transforming these types of knowledge into PCK. The role of self-reflection and collaboration with others was also found to be instrumental in PCK development. Having opportunities to develop all aspects of knowledge was not always available for participants in all situations. At times, there were PCK tasks that were beyond to scope of the given experience or participants were limited in their freedom to exercise their knowledge. This data demonstrates that participants needed opportunities and the agency to act on those opportunities to develop their PCK.