Purpose: The beliefs about this subject of N = 223 secondary education teachers were collected through an ex post facto research method using a descriptive and correlational design and a 27-item questionnaire. Design/methodology/approach: The arrival of online learning, in this case m-learning, to secondary education, has made educators in this stage incorporate digital resources, such as Smartphones or mixed reality (MR), to their classroom methodologies. The present study describes the results obtained in the project design, implementation and evaluation of MR materials in learning environments (PID2019-108933GB-I00). The starting general objective is to determine the perception of Compulsory Education teachers-in-training from the areas of Experimental Sciences, Engineering and Architecture, and Health Sciences, on the use of MR as a teaching tool under the m-learning modality. Findings: The main conclusion obtained was that neither sex nor age had an influence on the use of MR in the classroom, and its use was determined by elements associated with the classroom methodology, such as collaborative work and attention to diversity, which took place in the education center. Research limitations/implications The main obstacle found when conducting the research was being able to access the general population of teachers-in-training in the aforementioned Master's program. Originality/value: The value of the article lies in publicizing the knowledge that secondary school teachers have of MR and giving clues to create training actions that encourage its incorporation into the classroom methodology.