Background: Teacher practices when teaching mathematics are supported by their beliefs on how this subject should be approached. This has an impact on the learning of students who generally perceive mathematics as an incomprehensible mechanical activity in which a series of algorithms must be followed to obtain a solution. Therefore, the following questions arise: What are the beliefs of mathematics teachers regarding the teaching process? Which methodologies do they use in the classroom? Objective: The objective was to analyse the beliefs of elementary school teachers and secondary school mathematics teachers during the teaching process. Design: The study used a descriptive quantitative approach. Setting and participants: The sample consisted of 100 elementary school teachers and secondary school mathematics teachers from three regions in Chile. Data collection and analysis: Due to the Covid-19 health crisis, Google Drive was used to send a Likert questionnaire to each of the study participants. The information was processed and quantitatively analysed with the SPPS 25.0 statistical software. Results: Statistically significant differences were found based on specialisation, place of work, school administration, and gender of the participants. Conclusions: Teachers considered that knowing, learning, and applying mathematical knowledge was possible through rote and routine activities. In addition, teachers with 5 to 8 years of experience believed that mathematics develops problem-solving skills.