This article aims to understand the knowledge mobilized by Mathematics teacher educator and the challenges they encounter in their professional activities. The research is configured as a qualitative study, which used the teaching case study approach as a method for producing data. The information was collected through audio recordings with five teacher educator who work in the Pedagogy Degree courses at five federal universities in the country, with disciplines in the field of Mathematics Education. For analysis, the Discursive Textual Analysis method was used. In general, the indicators obtained indicate that beliefs and teaching models that they had influenced their professional choices. In addition, it was identified that there is a distance among students in understanding themselves as teachers who teach Mathematics, in a certain way, arising from the curricular structure of the courses, since there is little space for Mathematics, which is a great challenge in initial training.