Indeed, the lack of successful and effective leadership style of secondary school principals in the province of Sindh, particularly in Karachi has resulted poor performance and low students achievement. Therefore, the basic purpose of the study was to examine the leadership styles of the principals in secondary schools of Karachi. The scope of the study was limited to all the secondary schools of Karachi. Seven hypotheses were formulated for the study. Among these, six hypotheses were based on the demographic variables consisted on sex, status of schools, professional qualification, experience, age and marital status. The seventh hypothesis was related to item-by item analysis of the questionnaire on the thirty dimensions of the leadership styles. The population of the study was large and diverse, thus stratified random sampling was used. The total sample size consisted of 300 teachers and 100 principals from 100 schools. Two research instruments, a self-made questionnaire of 30 items and an interview protocol of 4 broad questions were used. In views of the principals, only one hypothesis out of six was rejected and five were upheld. It was concluded, (2) that private secondary school principals were more significant in the effectiveness of school organization than the government school principals. Though, in hypothesis number (1), (3), (4), (5) and (6), no significant differences were found between the leadership styles of male and female, trained and untrained, experienced and less experienced, younger and older, and married and unmarried secondary school principals in the effectiveness of school organization. In views of the teachers, four hypotheses out of six were rejected and two were upheld. It was concluded that in hypothesis number (1), it was found that the leadership styles of female secondary school principals were more superior to male principals in the effectiveness of school organization, (2) private secondary school principals were more superior to government secondary school principals, (3) trained secondary school principals were more superior to untrained secondary school principals and (5) younger secondary school principals were more superior to older secondary school principals in the effectiveness of school organization. Though, in hypothesis number (4) and (6), no significant difference was found between the leadership styles of experienced and less experienced and married and unmarried secondary school principals in the effectiveness of school organization. The collected data was analyzed through the ‘t’ test and ‘chi square’. In the light of the findings, several solid recommendations were made.