The need for companies to define sustainability-based strategies has gained more relevance in modern society. In lieu, this study examines environmental sustainability (ES), the implementation of circular economy (CE) practices, and their conceptual relationship with SME managers. The methodology employed is in-depth interviews applied to SME managers of Catalonia (Spain), a prominent business area in Europe. This study reveals the slow incorporation of ES in SMEs through CE tools such as recycle, recovery, and reuse in the final stages of their production process. The knowledge about CE tools and their potential, the low pressure from customers regarding environmental issues, and the lack of communication and incentives to adopt ES norms can explain this behaviour. The development of environmental public policies for SMEs and an ecosystem that allows the exchange of resources and collaboration help decrease these companies' overall resource use.