In this project, we are studying the development of the knowledge, skills and attitudes required by post-primary mathematics teachers to teach mathematical problem solving. The subjects of the study are pre-service mathematics teachers (PSMTs) in DCU, and the context is a module on mathematical thinking – with an emphasis on problem solving. Drawing on the conceptual framework of Chapman which identifies the different capacities required by teachers in order to teach mathematical problem solving, we are studying a range of linked issues: the problem-solving abilities of the PSMTs; their understanding of the nature of mathematical problems and of mathematical problem solving and problem posing; and their beliefs about mathematical problem solving and its role in learning mathematics. This mixed-methods project views the taught module as an intervention aimed at enhance these capacities, and is informing (and  studying) incremental improvements to this intervention.