This study investigated Principals' Perception of misconduct among Secondary School teachers in Delta State. Four research questions and four hypotheses were formulated to guide the study. The instrument used for collection of data was tagged "Principals' Perception of Teachers Misconduct Questionnaire" (PPOTMQ). For content validity, the instrument was given to some lecturers in the Department of Guidance & Counselling who scrutinized and made some corrections. The test-retest method of reliability was employed and the co-efficient of 0.72 was obtained. The sample consisted of 100 principals. The t-test statistics was employed to test the hypotheses at 0.05 level of significance. Results of the study revealed that absenteeism, lateness, truancy and poor quality teaching were perceived by principals as forms of misconduct in public secondary schools. Recommendations that were proffered include counselling tutors against indiscipline in all post-primary institutions in Delta state, Nigeria.