This paper presents issues related to the use of technology by secondary school pre-service mathematics teachers engaged in open mathematical modelling projects. Pre-service teachers developed these projects within a regular mathematics education course during the teacher education program at the university concerned. This environment, called a modelling scenario, is the context for our study, which is based on the analysis of projects produced by seven consecutive cohorts of pre-service teachers beginning in 2010. The research questions guiding our study seek to determine which technologies pre-service teachers chose, for which modelling purposes they chose them, and in which phases of the modelling process they were significantly used. During the modelling process, pre-service teachers used the Internet, spreadsheets, mathematical software and programming languages. The Internet, the most utilized technology, was used to find information or data, to select variables, or to formulate problems. The other three technologies significantly influenced the processes of mathematical solution and validation. The in-depth analysis of a single project shows an original use of visual affordances of technologies and a dialectical relationship between problem posing and technology use. The study enables us to conclude the necessity for coordinated action between mathematics educators and mathematicians to generate a deeper understanding of modelling as a pedagogical proposal and mathematical activity.