This study aimed to identify the motivational factors affecting the willingness of employees to share knowledge and examine intrinsic and extrinsic motivational factors and influences on attitudes toward knowledge sharing and explicit and implicit knowledge sharing intention. Planned behavior pattern is used as a theoretical framework. This research was conducted in two phases. First, factors were identified according to the literature review and exploratory interviews. Then the impact of each factor was evaluated in terms of structural equation modeling. This is an empirical research and the research method is descriptive survey. Data was collected using a questionnaire and interview. The study was on the staff working in administrative units of Tehran Municipality and the number of staff at the time of study was 2230. Cluster sampling method and sample size based on population and using Cochran formula of 328 people determined that 35 persons were not held accountable. To determine the reliability of questionnaires, Cronbach’s alpha coefficient was calculated to 0.824 which was found at a high level. Data was analyzed by SPSS and LISREL software. Finally, the proposed pattern was confirmed. The results showed that the intrinsic and extrinsic motivational factors influence on the attitude of employees and the attitude influence on tacit and explicit knowledge sharing intention. Also, extrinsic motivational factors influence on tacit knowledge sharing intention and intrinsic motivational factors influence on explicit knowledge sharing intention. Extrinsic motivational factors influence on explicit knowledge sharing intention and intrinsic motivational factors influence on tacit knowledge sharing intention by the attitude and tacit knowledge sharing intention influence on explicit knowledge sharing intention.