Prior research on the development of category-based reasoning indicates a protracted developmental course of this ability as well as a high degree of individual variability. However, the sources of this individual variability as well as the sources of developmental change remain unclear. The present study aimed to examine these issues, with a focus on the role of representational change and executive function development. Across two time points spaced approximately 7 months apart, children’s category-based reasoning was assessed along with a battery of executive function and representational change measures. Results replicated prior work in that only a small proportion of children exhibited spontaneous category-based reasoning at Time 1, and this proportion increased with development. In addition, both executive function and representational change were found to predict the development of category-based reasoning.