he aim of this study is to examine the 21st century skills competencies perceptions of prospective science teachers and their attitudes towards STEM as well as the relationship between these. In the study, relational screening model was used. The sample of the research consists of senior students from Science Education Departments of Fırat, Cumhuriyet, Erciyes, Muş Alparslan, Nevşehir Hacı Bektaş Veli Universities enrolled for 2016-2017 academic year. In order to collect data for the study, “21st Century Skills Competencies Perception Scale for Teacher Candidates”, developed by Anagün, Atalay, Kılıç and Yaşar (2016), was used for determination of 21st century skills perceptions and “STEM Attitude Scale”, developed by Faber et al. (2013) and adapted to Turkish by Yıldırım and Selvi (2015), was used for determination of attitude towards STEM. In the analysis of the data, diagnostic analyses, t-test, Mann Whitney U test (MWU) and Pearson Correlation analyses were used. According to research findings, it was determined that prospective teachers agree, in a level higher than moderate, with “learning and innovation skills”, “life and career skills” and “information, media and technology skills” which are dimensions of the 21st century skills. Significant results were obtained based on gender variable regarding perception of “life and career skills” and “information, media and technology skills” dimensions of 21st century skills competencies, in favor of female prospective teachers. It was determined that prospective teachers have positive attitude towards STEM. No significant difference was observed based on gender regarding attitude towards STEM. It was found that there is a low and moderate positive relationship between “Teacher Candidates’ 21st century Skills Competence Perception and “STEM Attitude Scale” subscales. Based on the findings of the research, proposals for improving 21st century skills and STEM trainings were presented in teacher training programs.