Successful implementation of industrial symbiosis is highly complex and occurs across multiple dimensions, both internal and external to the firm. We interrogated twenty-five case studies to build a rich picture of the various approaches that have been adopted to foster resource synergies between organisations. In this chapter, we present a set of critical success factors which we categorised as enablers and barriers in regard to the implementation of industrial symbiosis. The lessons learnt illuminate the processes of consideration, facilitation and scale up of industrial symbiosis.