The aim of this study is to investigate the opinions of the secondary and high school mathematics teachers and mathematics teacher candidates who have been educated about HTTM learning process and experienced HTTM activities in the classroom environment about HTTM learning process. The study is a basic qualitative research study conducted with a qualitative understanding. The sample of the study consisted of three secondary school maths teachers working in different secondary schools and three high school math teachers working in different high schools in Turkey during 2016-2017 academic year, five senior class students who are secondary school mathematics teacher candidates taking teaching practice course and applying teaching practices at different secondary schools and five high school mathematics teacher candidates applying teaching practices at different high schools. The data of the study is comprised of video analysis of the interviews conducted through semi-structured interview form with the secondary and high school mathematics teachers and mathematics teacher candidates. Content analysis technique was used in the research. As a result of the data analysis, a two-dimensional structure related to HTTM learning process was obtained. In the first dimension of the findings 15 themes were obtained. These are preparation, time, flexibility, interdisciplinary nature, contemporary skills, technology integration, history of science integration, working with groups, metacognitive skills, conceptual understanding, projects, problem posing, motivation, evaluation and teacher competency. In the second dimension of the findings; benefits, difficulties and suggestions related to 15 themes were put forward.