Teachers’ conceptual understanding of elementary mathematics is believed to be fundamental to effective classroom level mathematics reform. This study examined preservice teachers’ change in conceptual mathematical knowledge after taking a reform-based mathematics methods course as part of a teacher certification program, and investigated the relationship between this change and factors such as preservice teachers’ academic background, initial levels of conceptual and procedural mathematical knowledge and values, and the number of mathematics courses taken in high school and university. The results of this study suggest that the number of mathematics courses taken in high school may influence growth in conceptual mathematical knowledge, while preservice teachers’ subject-area background and the number of university mathematics courses taken did not appear to influence growth in conceptual mathematical knowledge as needed to teach in a reform-based manner.