The aim of our research paper is to develop the economic principles for modelling the new trend in the economic relations called “sharing economy”. Sharing economy which is a product of social, economic, societal, and technological changes recently emerging and shaping up in the human society is marked by a high penetration into all sectors of the “traditional” economy. The rise of the Internet and the popularity of smartphones enabled its high effectivity and usage, while the rise of the creative economy and “gig” economy made its application very easy to handle. Our paper is based on the methods of institutional analysis. We obtain a number of valuable theoretical results that can be summarized as follows: First, the model of sharing economy has been examined, the main agents of interactions have been identified, among which state structures, digital platforms and companies creating them, as well as citizens themselves, actively participating in economic activities are singled out. Second, transaction costs for the most common types of transactions (peer-to-peer) were determined. Sub-transaction costs (for example, information retrieval), transaction costs in the transaction process, as well as post-transaction costs (for example, reputational costs) are noted. Third, the principles of institutional modelling of sharing economy from the perspective of its effectiveness are defined, a typology of institutions of sharing economy based on the model of interactions of economic agents is proposed. Our results and outcomes might be useful for helping to shape up the rules of the game for the use of sharing economy in the modern economic relations and might be applied by the researchers, stakeholder and policy-makers alike.