This research was conducted with the aim of investigating the effect of leadership styles of managers on the academic performance of students in secondary schools in Tabriz. In this study, descriptive-correlation research method was used. The statistical population included all principals and students of secondary schools in Tabriz city in the academic year 1402-1403. A sample of 250 managers and 1000 students were selected using multi-stage cluster sampling method. The research tools included the Multifactor Leadership Style Questionnaire (MLQ) and students' academic performance scores. Data were analyzed using Pearson correlation and multiple regression statistical tests. The results showed that there is a positive and significant relationship between managers' transformational leadership style and students' academic performance (r=0.68, p<0.01). Also, the transformational leadership style could explain 46% of the variance of students' academic performance. The findings of this research can be used in educational planning and development of leadership skills of school principals.