Knowledge sharing is a complex behavior. To show this complexity and ways of improving it, the intermediary role of attitudes, cognitive norms, and motivation seem to be important when considering the interaction between this complex behavior and personality traits. To show this relationship, a sample of 357 teachers from among all 570 high school teachers in Birjand was selected and then given two questionnaires on knowledge sharing behavior and personality traits. The collected data were analyzed through path analysis where in the chains of personality traits, attitudes, motivation, and behavior; personality traits, cognitive norms, motivation, and behavior were established. Hence, the main hypothesis regarding the intermediary role of attitudes, norms, and motivation was supported. Furthermore, the respondents consider knowledge sharing behavior as important since it helps them learn and expand their knowledge. There was no significant difference between male and female teachers in these regards.