The main purpose of this study was to examine pre-service secondary mathematics teachers' (PSMTs) levels and development of technological, pedagogical and content knowledge (TPACK). In line with this purpose, this study was designed to use teaching experiment methodology within a course. The participants of the study were 28 fourth grade PSMTs. The qualitative research paradigm was adopted and the teaching experiment methodology was used in the study. By using this method, PSMTs were taught about how to integrate technology into mathematics education, how to use various mathematics and geometry dynamic software, interactive applications that are used in mathematics education, various websites and technological tools related to education during 16 weeks and four hours in each week. The data was collected during the experiment, and analyzed by using content analysis and document analysis methods. The results show that PSMTs' technological knowledge, technological pedagogical knowledge, technological content knowledge and TPACK levels were developed by applying the teaching experiment methodology. Particularly, when the activities they designed, lesson plans, reflections and free writings were examined in detail, it was observed that PSMTs' skills about how to integrate technology in order to ease the learning and teaching of mathematics and utilizing it were developed. Within this context, it is thought that technology integrated courses or technology based courses should be embedded or the context of these courses were developed in the teacher education programs.