Today, organizational knowledge is recognized as a very valuable intangible resource for gaining a competitive advantage. Managing such intangible assets is essential for maintaining and gaining a competitive advantage for organizations, especially knowledge-based companies whose survival and success are tied to knowledge. Knowledge can improve and enhance the performance of organizations when shared across the organization. Despite the vital role of internal knowledge sharing, little research has been done on the factors affecting knowledge internal knowledge sharing in knowledge-based companies. For this purpose, in the present article, first, by reviewing the background, the factors affecting the internal organizational knowledge sharing in organizations were extracted, and then, using the DEMATEL method, the relationships of these factors and their prioritization have been studied. The present study is a descriptive and survey research and is a tool for collecting secondary data (library studies) and primary data (questionnaire). After designing the questionnaire and confirming its validity by experts, the questionnaire was distributed and filled by 30 experts and managers of knowledge-based companies located in S&T Parks of Shahid Beheshti University, University of Tehran, and Tarbiat Modares University. The research results show that formal and informal procedures, open-door policy, and knowledge sharing strategy are the most influential factors and in contrast to communication and network, people's knowledge and interactive memory system are the most influential factors.