The present study was aimed to explore the association of head teachers’ leadership styles with school effectiveness. Research was descriptive and the survey method was used to explore the phenomenon. All the teachers serving in Federal Government (FG) Secondary Schools in Islamabad were taken as the population and researcher prepared a sample frame and 50 schools randomly. A sample of 300 teachers was selected in such a way that from each school six teachers were conveniently taken. Questionnaire was developed through an extensive review of the literature to collect perception of teachers about leadership styles and school effectiveness. Findings revealed that the majority of the principals in federal schools had practiced autocratic and democratic leadership styles. Meanwhile there was a significant relationship between leadership styles and school effectiveness also seen. Results indicate that teachers perform better in those schools wherein the principals make use of an autocratic and democratic leadership style. It was recommended that principals as the leaders should make use of the best fitted style that helps collective responsibility and consultative decision making with all schools concerned.