For a long time, Facilities Management has been marginalized in the realm of management. With the enlargement of the scope of Facilities Management and the emphasis of its strategic influence on business, there has been increasing concern on the social context of Facilities Management. Outsourcing, as a management method, is commonly practiced in this area. It has been demonstrated in relative studies that collaborative outsourcing relationships lead to outsourcing success. This paper will shed light on outsourcing relationships between clients and suppliers of Facilities Management services from a social interaction perspective. It aims to explore the factors that affect outsourcing relationships on an interactive level and their manifestation in the outsourcing process. A generic model of outsourcing success will be developed based on a thorough review of the relevant literature. Case studies will be conducted in order to illustrate the model and to explore further findings.