This study investigated the relationship between principals’ performance tasks and Teachers’ job performance in Osun State Secondary schools. It was a descriptive research of the survey and ex-post facto designs. Simple random sampling techniques were used to select the 50 secondary school principals and 400 teachers in the state. Questionnaire tagged principals administrative tasks performance (PATQ) Teachers Job performance (TJPQ) were used to elicit information from the respondents. The reliability coefficients of 0.74 was obtained. The data collected were analysed using simple Percentages, Means and Pearson Product Moment Correlation. Hypotheses formulated were tested at 0.05 level of significance.  It was revealed in the study that principals administrative tasks had significant impact on teachers job effectiveness in Osun State.  The study revealed that proper monitoring of teachers Instructional activities was the most prevalent administrative task. The level of teachers job performance is moderate as revealed by the study. However it was recommended that principals should regularly monitor teachers in the classroom teaching and monitoring them where necessary. This will assist them to improve their effectiveness in instructional delivery. Principals’ should regularly attend workshops, conferences, seminars to improve their leadership roles.

They should be acquainted with required managerial functions in order to perform their administrative duties and functions effectively and efficiently. The use of goal-oriented supervisory techniques by principals in schools is crucial to improvement of teaching and learning processes.

KEYWORDS: Principals, Administrative effectiveness, Teachers Job performance, Productivity, Human Relations.