Many teachers' experiences in problem-based classrooms are limited, therefore, mathematics teacher educators face a significant challenge when trying to inspire in-service teachers (ISTs) to teach through problem solving. To address this challenge, the professor in a mathematics education course designed and implemented an instructional model using the following principles as a guide; modelling problem-based instruction, creating opportunities for reflection, and building a discourse community. Assessment results showed that ISTs were better able to create problem-based lessons after going through the instructional model. Additionally, an analysis of writing samples revealed several changes in ISTs' thinking. Most notably, ISTs discussed a new role for communication in the classroom and emphasised the need for students to develop their own solution strategies. Their writing also provided evidence that participation in problem-based learning and critical reflection during the instructional model were key factors that led ISTs to think differently about instruction.