This study investigates how the use of different graphing calculator models influences the mobilization of mathematics teachers’ professional knowledge. Based on the KTMT model - Knowledge for Teaching Mathematics with Technology - we analyzed how solving the same mathematical task using different graphing calculators (Casio fx-GC50, Numworks, TI-84 and TI-Nspire) can require the mobilization of different domains of the teachers’ professional knowledge. Specifically, considering the teaching of functions in 10th and 11th grade (16–17 years old), we intend to analyze the relationship between the specific domains of the KTMT model and the integration of the different models of graphing calculators (GCs). With this as our focus, we seek to answer the following research questions: (1) How do the specific characteristics of each GC model influence the mobilization of the different KTMT domains?; (2) How does the specific model of the graphing calculator influence the mobilization of the different knowledge domains? The methodology adopted is qualitative, with an interpretative approach, based on the case studies of three Mathematics teachers who have extensive experience in the use of GCs. Data were collected through interviews and class observation, with the analysis guided by the KTMT model. The results show that the mobilization of the different domains of the KTMT model changes according to the GC selected, and that the specific characteristics of each model influenced the teachers’ pedagogical decisions.