Although the effects of professional development programs on teachers' noticing skills have attracted considerable interest among mathematics education researchers, little is known about the developmental process of prospective teachers' noticing skills within initial teacher education. This paper examines the extent to which prospective teachers' noticing skills are developed through the mathematics education courses taken within the mathematics teachers' education program using exemplarily the topic division of fractions. The study is grounded on the framework of Professional Noticing of Children's Mathematical Thinking which specifies three facets of noticing, that are attending, interpreting, and deciding how to respond. Twenty-two prospective mathematics teachers (PSTs), who were enrolled in the Middle School Mathematics Teacher Education Program at a Turkish university, participated in this study. The results revealed that most PSTs gained expertise in all three kinds of noticing skills during their teacher education. The highest progression could be identified in the interpretation skills and the lowest in attending skills. These results are important for initial teacher education programs, highlighting that general, non-specialized mathematics education courses within initial teacher education have the potential to provide an efficient professional development program to develop PST's noticing skills. The study points out that further research is needed in order to provide additional details about how teacher education programs could be redesigned and implemented to ensure opportunities for PSTs to develop noticing skills within all three facets leading to robust or at least substantial evidence of all three noticing skills.