In South Africa teachers are faced with the introduction of yet another revised curriculum. Higher education institutes are developing programmes to help teachers through the transition. This article describes such an intervention. The research addresses the question: how could mathematical reasoning cartoons be used as a tool to support teacher ownership of curriculum change? The article reports on three action research iterations in which qualified and experienced mathematics teachers are introduced to the use of reasoning cartoons during a short learning programme targeting the development of teachers' ownership of curriculum change. Rainer and Matthews's ownership of learning framework is adapted and used as a theoretical lens to provide indicators of teachers' ownership of curriculum change. Data were collected from audio-taped discussions in groups and teachers' written reflections concerning the introduction of reasoning cartoons, using the tenets of exploratory talk, into their classes. The results indicate that, after the first iteration, where cartoons developed commercially in the UK were introduced, teachers demonstrated that they could move from a didactic to a dialogic environment where spaces were created for all participants to speak and to listen. When cartoon content was drawn from the current South African curriculum, the teachers were able to introduce a largely teacher-centred approach to implementing the curriculum. However, it was only when the teachers took ownership of their own cartoon construction that they manifested the majority of indicators of ownership of curriculum change. The research suggests that teachers can use a mediating artefact to enable them to embrace curriculum changes imposed from the top down.