The paper appraises the principals' role and the perception of teachers in selected public secondary schools in Osun State of Nigeria. The paper specifically investigates the principals' role performance and the teachers' perception of the same role (instructional, administrative and human relations) in the selected public secondary schools. The survey research design was used for the study. The population consisted of the principals and the teachers in public secondary schools in Osun State, Nigeria. Altogether 210 respondents were sampled comprising 175 teachers and 35 principals randomly selected from the six geo-political zones (Iwo, Ikirun, Ife, Ilesa, Osogbo and Ede) in Osun State. Thirty-five (35) schools were randomly selected from the list of all the secondary schools in the six zones in Osun State. Two sets of questionnaire were used for data collection. These were: Principals' Role Performance Questionnaire and Teachers' Rating of the Principals' Role Performance Questionnaire. The data collected were analysed using descriptive statistics. The results showed that about 78% of the principals claimed to perform the administrative role very well while 62.5% and 59.4% performed the human relations and the instructional roles respectively. However, the rating of teachers showed that only 37.5% of the principals actually performed the instructional role, 70.9% performed the administrative role while 64.5% performed the human relations role in the schools. The general view of the teachers on the principals' actual performance of their role is that principals perform more of administrative role and human relations role than instructional role in the school. It was concluded that promoting and intensifying the instructional role of the principal is capable of enhancing the students' academic performance in schools.