In recent years there has been an increase rate of awareness about the occupational stress and its effects on work competencies. The teaching profession is one of the sensitive profession on which the future of any country depends. As far as Pakistan is concerned teachers and teaching both are unfortunately not enjoying very good and healthy social and financial status. Thus the study was designed to examine the determinants of occupational stress among secondary school teachers. Main objectives of the study were: to examine the occupational stress of teachers teaching at public and private secondary schools and to identify the reasons of occupational stress among teachers of secondary schools. In order to achieve the objectives of the study   the researcher selected descriptive style. The population of the study was comprised of all the teachers teaching in the public and private secondary schools of Rawalpindi and Islamabad. Random sampling was used to draw representative sample from the population. Four public and four private secondary schools for boys and girls were selected randomly. The sample size was comprised of two hundred teachers.  David Fontana Professional Life Stress inventory and inventory used in UCU Health and Safety by John Bamford was adapted.   Findings of the study revealed that private school teachers have significantly higher level of professional life stress as compare to the teachers of public schools, job is the major cause of occupational stress, and teachers were not satisfied with their role in schools which is one of the determinants of stress.