The aim of this study was to investigate the correlational and causal relationship between middle school students’ entrepreneurial competencies and science, technology, engineering and mathematics (STEM) attitudes. A total of 648 middle school students (seventh and eighth grade) participated in this study. STEM attitude scale and two entrepreneurial competency scales that were developed in different studies in the literature were used as data collection tools. In addition, a simple regression, a multiple regression and a stepwise multiple regression analysis were executed to analyse the data. The correlational analysis showed that there was a moderate level, positive correlation between the STEM attitudes of students and their overall entrepreneurial competencies. Also, the multiple regression analysis showed that entrepreneurial competencies consisting of professionalism, risk-taking, creativity and tenacity explained 41% of the change in STEM attitude. The stepwise multiple regression analysis indicated that professionalism predicted the most the STEM attitude statistically more.