Professional development of educators, especially in preschool years has been neglected in Iran. The purpose of this study was to investigate the viewpoints of experts and teachers about the purposes and content of the professional development plan for preschool teachers. This research is a descriptive-analytic study conducted through both qualitative and quantitative methods. The statistical population included academic members of universities, PhD students, psychology instructors and teachers of preschool curriculum and education. In the qualitative part, the sample was selected via purposeful grid methods and the teachers were selected through stratified random sampling. The data were collected via semi-structured interview and researcher-made questionnaire. To estimate the validity of the interview and the questionnaire, content validity method was used, and to estimate their reliability, Cronbach's alpha was utilized. Qualitative findings were categorized using content analysis; quantitative findings were analyzed via inferential and descriptive statistics. The results of the Friedman's test demonstrated that, according to teachers, becoming an active and responsible teacher has the highest importance in the development plan, while identifying parents' and societies' expectations as well as interacting with them has the lowest importance. In the content, professional development of teachers, class management and settling problem in class are the first items in terms of importance; yet familiarity with contagious diseases in childhood and controlling them have the lowest level of importance.