Coding has been introduced into K-12 classrooms around the world. In Ontario, coding is now a mandatory component of mathematics curriculum. Teacher education programs need to ensure preservice teachers feel adequately prepared to support students with learning coding, and in particular, coding within mathematics classrooms. This study investigates how perspectives about teaching coding and mathematics of preservice teachers, who were enrolled in a 36-hour course evolved as a result of: (a) course experiences; and (b) mathematics and coding teaching experiences. Across six years, six cohorts of preservice teachers attending an Ontario University were enrolled in a course called “Computational Modelling in Mathematics and Science Education”. The 53 participants who were selected for this study were in their first year of a Bachelor of Education program and taught mathematics and coding as part of a final assignment in the course. The study was guided by a constructivist theoretical framework. Qualitative research methods were used to explore participants’ course and teaching experiences and reflexive thematic analysis was incorporated. The study found that the preservice teachers underwent four turning points, which involved shifts in their perspectives about teaching and learning mathematics and coding. Seymour Papert’s theory of constructionism, and Yasmin Kafai and Quinn Burke’s computational participation framework, were used as lenses to analyse the turning points. The study presents the findings as recommendations for practice. In doing so, it offers a model for teaching coding that may support both teacher educators and researchers.