The purpose of this study is to examine the effects of STEM practices on the selfefficacy, pedagogical and content knowledge of pre-service teachers. Thus, the study group consists of 20 pre-service science teachers The study is designed in accordance with the convergent parallel design among the mixed research method designs. In this design, qualitative and quantitative data are collected simultaneously. In this present research, the "Pre-service teacher interview form" and "SELF-efficacy belief scale in science teaching" were used as data collection instruments. Whereas the content analysis was conducted in the analysis of qualitative data, SPSS package program was implemented in the analysis of quantitative data. As a result of the analysis of the qualitative and quantitative data obtained, it was concluded that STEM practices positively improved the belief in the self-efficacy of pre-service teachers. In addition, the results indicated that STEM practices had positive effects on the content and pedagogy knowledge of the pre-service teachers. Based on these results, studies that examine the effects of STEM practices on the pedagogical and content knowledge of teachers can be included