The present study emphasizes on the role of Principals in improving Teachers' Professional Development (TPD). The first objective of the study was to explore the role of principals as instructional leaders in TPD. The second objective was to compare the role of principals as instructional leaders in improving TPD as perceived by the Principals and Secondary School Teachers and the third objective was to compare the role of principals (instructional leaders), in improving TPD in the perspective of southern districts of Khyber Pakhtunkhwa. The researcher adopted a quantitative research design for the study. A questionnaire was used for the data collection process. The population consists of principals/headmasters (413) and secondary school teachers (1523), which working at the secondary school level. All the principals and teachers were taken as the main population for the study. A stratified sampling method was used to select the sample from the whole population of 332 (18 Percent), in which there were 68 Principals and 264 SSTs. The result indicates that school principals have a noteworthy role in improving TPD.