This article discusses how a preservice teacher of mathematics develops and mobilizes their didactical knowledge, in the matter of mathematical content and of instructional knowledge, in the preparation and analysis of tasks of mathematical modeling, using technology. The work took place at the end of their initial education when they make their internship. It is an interpretive study in the form of a qualitative case study that shows that the performance of tasks of mathematical modeling and the thinking about it, using technology, during the internship it is an opportunity for professional development of the preservice teacher, both the level of their knowledge of the mathematical content, enabling knowledge worker during their initial training, as their instructional knowledge. At this level, the modeling task allowed the future teacher to understand that beyond the transmissive model, there are other models of teaching in an exploratory nature, in which the teacher proposes mathematical open tasks with a higher degree of difficulty, involving students in mathematical intense activity which may result in significant mathematics learning.