The pre-service teacher followed in this paper aimed to act as an agent of change during a time of reform in Irish secondary mathematics education. A teacher-researcher led action research project was conducted to depict the reality of the situation regarding the implementation of mathematical problem solving from a variety of perspectives-namely those of the pre-service teacher/teacher-researcher, the secondary school students, and the other mathematics teachers in the school. A problem-based approach to teaching and learning was implemented by the pre-service teacher using Van de Walle's teaching through problem solving framework in an attempt by the pre-service teacher to enact change at the classroom level. Following this intervention, participating students showed an improvement in engagement with mathematical problem solving and expressed positive opinions regarding the problem-based approach to teaching and learning. Meanwhile, other mathematics teachers in the school expressed concerns relating to the reality of implementing problem solving in their classrooms; however, these concerns were not issues faced by the author when implementing problem solving in the same setting. When these concerns were indirectly challenged by the preservice teacher a change in conversation occurred.