Industrial symbiosis has proven to be an important tool for improving business sustainability with numerous environmental, economic, and social benefits. The literature on this subject has been provided with countless case studies of the application of this practice in different geographical locations. However, studies concerning Portugal in this area are still scarce. Thus, this article aims to map and analyze the existing cases of industrial symbiosis in Portugal, as well as the current state and the legislative context regarding this practice. It also aims to analyze the main barriers to the growth of synergy relations and outline new paths for the development of industrial symbiosis in Portugal. From the analysis to the case studies, it was possible to conclude that most industrial symbiosis networks have few actors, and networks with two and three are common. However, owing to strategic plans, the type of existing economic activities, and the waste generated, there is much potential for industrial symbiosis networks to be established and to contribute to emission reductions, more efficient use of resources, and reduced external dependence. However, in order to increase industrial symbiosis, concerted action must be taken at various levels to encourage companies to develop synergy relations. Changing the legislative framework, making funds available, the role of local governments, the existence of a facilitator, and the use of some industries as anchor tenants are some of the aspects that can contribute to the increase of industrial symbiosis in Portugal.