The aim of this study is to examine the mediating role of subjective well-being in the relationship between instructional leadership behaviors of school principals and teachers' professional engagement through structural equation modeling. The study was conducted with 238 teachers working in Batman province in the 2019-2020 academic year. Two different methods were used to determine the sample. First of all, it was taken into consideration that the teachers had been working with the current principal for at least 6 months (criterion sampling) and teachers who met this criterion were reached through convenient sampling method. As data collection tools, "School Principals' Instructional Management Rating Scale", "Teachers' Professional Engagement Scale" and "Teacher Subjective Well-being Scale" were used. The findings showed that teachers perceived the instructional leadership behaviors of school principals as sufficient. Additionally, teachers' subjective well-being and professional engagement are high. It was also found that instructional leadership is a significant predictor of subjective well-being and subjective well-being of professional engagement; however, it was determined that instructional leadership did not significantly predict professional engagement. Subjective well-being has a mediator role in the relationship between instructional leadership and professional engagement. The findings which are anticipated to contribute to existing literature are discussed and based on them some suggestions are made for both policy makers and practitioners.