This paper studies the evolution of the theory of the economic mechanism, the features of its implementation in economic models of certain countries. It was proved that during the formation of economics there weren’t any economic mechanism theories. The scientists considered separate economic categories, which according to modern interpretations are the elements of the economic mechanism. The purpose of this article is to analyze the views of representatives of economic schools on the theory of the economic mechanism, to show the existence of specific features of its implementation in different countries, depending on their institutions. To achieve the purposes the tasks have been set: to determine the contribution of the main economic schools in the development of the concept of an economic mechanism; to clarify the concept of the category of the economic mechanism; to substantiate the role of formal and informal institutions in the development of the economic mechanism of economic systems; to give a comparative description of the economic mechanism of some developed countries: the USA, Germany, Sweden, Japan, on the basis of formal and informal institutions. The article clarifies the concept of the economic mechanism category. It is shown that the nature of the economic mechanism is determined by the complex of the industrial relations and the level of productive forces development. At the same time the features of the economic mechanism depend on the laws and regulations applied in the economy of specific countries. The article proved the decisive importance of formal and informal institutions in the development of the economic mechanism of national economies as important tools for economic relations regulation, the consistency of which leads to the development of effective economic mechanism displaying the economy on an innovative way of development. The article used the system, dialectical, institutional-evolutional and other approaches and methods of research.