This chapter examines the case of the LEAL & SOARES SA from Portugal, through its SIRO® brand, as an example of how a small and medium size enterprise (SME) can operationalize the sustainability and circular economy principles. Existing research tends to focus on large corporations’ sustainability practices offering limited insights into the organizational processes, barriers, and enablers shaping circular transitions at the SME level. This chapter addresses this gap by applying a qualitative case study, combining semi-structured interviews, document analysis, and a Delphi-based validation process, to examine how the company embeds circular business models within its operations. The case highlights practical approaches to performance measurement and demonstrates that hybrid circular business model adoption and industrial symbiosis can enhance both environmental resilience and economic viability in resource-intensive SMEs. Overall, this chapter contributes to the literature by providing empirical evidence of advanced circular practices in SMEs and offers managerial insights for embedding circularity strategically. The study also underlines the potential for generalizing these solutions, while adapting them to different economic sectors, thus reinforcing the broader value of the proposed analytical approach.