The purpose of this study is to examine the relationship between middle school students' attitudes towards STEM and their engineering knowledge levels in the sample of Uşak Province. The survey method was used in the study. A total of 723 students participated in the study by using the stratified sampling method. STEM attitude scale and Engineering Knowledge Level Measurement Scale (EKL) questionnaires which were adapted into Turkish by Aydin, Saka, and Guzey (2017, 2018) were used for data collection. The statistical analyses revealed that while gender and grade level did not make any significant difference with respect to STEM attitudes, a significant difference was found in favor of female students in terms of EKL. The only significant difference was revealed in 8th-grade students with respect to EKL. Finally, a weak correlation among 6th, 7th, and 8th-grade students' attitudes towards STEM and EKL was revealed.