Transaction cost, the cost that is not considered in the production function of the business, is actually the success or failure of the market. Examining various international reports (such as the Doing business, competitiveness, and global entrepreneurship monitoring) as well as the evidence and current status of Iran tourism indicate high transaction costs and inadequate business environment. Accordingly, the institutionalism explanation of the factors affecting the market transaction costs and tourism businesses is the main object of this study. Based on this, using the qualitative approach (theme analysis) and the profound interview with tourism market experts, the factors affecting the Iran tourism market transaction costs based on the model of new institutionalism have been identified and analyzed. The results of this survey indicate that the six themes identified in the study include the costs of information and knowledge, technology, business start-up, macroeconomic environment, capital and the cost of contracts, are the main elements of transaction costs of tourism in Iran and its impact has led to internalization, the lack of growth in the size of businesses and the reduction of partnerships among the players in the tourism industry.