(1) Background: Generally, firms are reluctant to report outsourcing failures, no matter what industry they operate within. To eliminate poor performance of outsourced service providers, it is necessary to establish a specific outsourcing relationship model for facilities management (FM). The purpose of this paper is to study the concept of outsourcing relationships in relation to FM and to investigate the design of the critical success factors on sustainable outsourcing strategies through a discussion of four dimensions (ownership of FM assets, control of FM assets, competitive position and long-term plan). (2) Methods: Based on two questionnaire surveys, data were collected from 38 clients and 34 service providers. The study evaluated the FM outsourcing strategies from critical success factors in educational facilities in Hong Kong. (3) Results: This study explains the impact of FM outsourcing strategies on Hong Kong’s four commonly outsourced FM contracts including building maintenance, security, cleaning and catering from the clients’ and service providers’ point of view. (4) Conclusions: This is the outsourcing way forward in order to create a better working environment conducive for all the parties that would result in better sustainability of FM’s future and thus impact the economic objectives of sustainable development, in parallel with adding social and environmental value.