This study aims to explore middle school students' attitudes towards STEM fields and their interest in STEM careers in terms of gender. Furthermore, this study examines the relationship between middle school students' attitudes towards STEM fields and their interest in STEM careers. Seven hundred and seventy four students from 10 cities located in 6 geographical regions of Turkey completed the STEM Attitude Scale and STEM Career Interest Survey. It was determined that middle school students' attitudes towards STEM were not statistically significant in terms of gender. In addition, it was found that students' interest in STEM careers differed in terms of gender. When the scores of attitudes towards engineering and technology fields and the interest in careers in these fields were compared in terms of gender, significant difference in favor of male students was found. Furthermore, a positive correlation between the middle school students' attitudes towards STEM fields and their interest towards STEM careers was determined. Results indicate that approximately 43% of the total variance of interest towards STEM careers stems from attitudes towards STEM fields. The results obtained from this study will give an insight into how to shape the aims and applications of the future STEM education programs.