The aim of the article is providing the scientific rationale for theoretical and methodological bases of forming and implementing the institutional and economic mechanism of wholesale enterprise operation. As a result of the study there generalized theoretical and methodical bases of the concept of «mechanism» with respect to wholesale trade, and it is concluded that scientific literature does not present its uniform interpretation. The most common in the economic theory and practice of wholesale enterprises types of mechanisms are identified, and their essence in terms of functional orientation is revealed. There presented a conceptual structure of the institutional and economic mechanism of wholesale enterprise operation taking into account the complex nature of trade and intermediary relationships, their peculiarities concerning production areas, exchange, distribution and consumption. The essence of the mechanism elements, relationships between them, the implementation sequence and feedback are defined as well. It was found that the main driving force of the institutional and economic mechanism of wholesale enterprise operation is subjects that operate depending on their own motives. According to the subject composition, economic and institutional motives are determined. With consideration to the composition and motives of the subjects, there defined objects of the institutional and economic mechanism, which are divided into groups comprising those that form economic incentives and the ones that create an institutional basis for wholesale enterprise operation. To ensure effectiveness of the institutional and economic mechanism, there singled out functional blocks that justify its goals and objectives (strategic and managerial block); functions, methods, and measures (operational block); spheres of mutual influence (block of interaction).