The paper aims at examining the hypothesis that the influence of trust on contract can be thought of as a dynamic factor of organizational choices in supply chains. The relationship between contract and trust is delineated on the basis of institutional environment, contractual incompleteness, safeguards and restrictive provisions. The interaction between individual and system elements in the formation of trust and its influence in hybrid contracting is considered. According to a New Institutional Economics approach and a theoretical framework is proposed. Empirical evidence is provided by a case study regarding an Italian retailer company establishing hybrid structure with its suppliers. Investments in suppliers selection provide the basis for trust supporting relationships which economize on negotiating and litigation costs.