Recently, scholars have started unpacking teachers' technology-related decision-making via the conceptual lens of pedagogical reasoning. Answering to the call for more domain-specific reasoning studies, this study explores secondary school mathematics teachers' pedagogical reasoning underlying their technology-mediated practice. By means of an open-ended survey, 30 Flemish secondary school mathematics teachers' technology integration practices were explored. Results show that teachers strongly value technologies that help them in (a) efficiently managing teaching and/or learning activities or (b) effectively attaining learning goals and meeting students' learning needs. In contrast, technology-usage to engage or extend students' learning was limited. In addition, although teachers report using a plethora of different type of technology tools, teachers most frequently mention using mathematical action tools, which help them to visualise mathematical ideas as well as to save time during instruction. To conclude, this study puts forward theoretical recommendations for future research as well as practical suggestions to foster (student-)teachers pedagogical reasoning.