Introduction. Nursing instructors, in addition to having faculty members' responsibilities such as teaching and doing research, offer community services as well. These responsibilities often cause great amount of job stresses for them. The purpose of this study was to determine the stressors in clinical and theoretical nursing education on nursing instructors.Methods. This descriptive-analytical study was performed using a questionnaire as data collecting tool. The research sample included 96 faculty members from nursing and midwifery faculties in Tehran who were selected by simple stratified sampling method.Results. The results of this study showed lack of preparation and educational experience in theoretical teaching, and heavy workload caused by teaching theoretical and clinical courses, administrative responsibilities and inequality feeling, in clinical teaching were the most stressful factors. Also, in theoretical teaching, large class size, working with faculties having different habits and values and keeping professional knowledge according to new sciences and professional development caused a high degree of stress. Moreover, providing sufficient individual supervision for each student, unclear policy regarding substitute instructor in time of sick leave or vacation and lack of preparation and experience, in clinical teaching were other stressful factors.Conclusion. Many factors in clinical and theoretical courses have been identified as stressors. It is recommended, theoretical nursing courses be taught as team teaching, and experienced instructors work with instructors with less experience. Also, educational programs should be planned in a way that nursing instructors with administrative responsibilities teach less theoretical and clinical courses.