The professional development is an emerging area to increase the performance in different fields. The professional development of a teacher is the professional growth that he/she acquires as a result of his/her experience and systematic analysis of his/her own practice and through participation in training activities. The purpose of this research was to compare the performance of professionally developed and undeveloped teacher and identification of significant professional development variables that can help the teachers to increase their performance. A convenient sample of 260 respondents (school teachers) from 49 secondary schools in 13 districts of Balochistan was taken to determine the major factors showing their effect on the overall performance of teachers. An instrument consisting of two parts, Part (A) (Professional Development of Teacher) and (B) (Performance Evaluation of Teacher), was used. All variables measured on likert scale. General Linear Model was used to find out the effect of training variables on the overall performance of teachers. The demographic characteristics of teachers with the interaction of professional development program variables were found significant in increasing the performance of teachers. This research study concludes that professionally developed secondary school teachers with new teaching methodologies, techniques, styles and new knowledge perform more as compare to those teachers who are professionally undeveloped or lack opportunities, interest or deliberately avoid participation in training activities.I am submitting my thesis on "Comparison between performance of professionally developed and undeveloped teachers: A study of public sector secondary school of Balochistan", as a thesis. As per the requirements, the thesis includes problem statement, the primary data along with literature review, development and testing of hypotheses.