Small and medium-sized enterprises (SMEs) are key actors in the shift toward a circular economy (CE), yet how they adopt CE principles remains inconsistently understood. This study systematically reviews 25 peer-reviewed publications from 2014 to 2024 indexed in Scopus, spanning disciplines such as Business, Environmental Science, Engineering, and Social Sciences. Using the TCCM (Theory–Context–Characteristics–Methodology) framework alongside bibliometric analysis via Biblioshiny and thematic synthesis, the review uncovers recurring CE practices—including eco-design, closed-loop systems, and digital performance tools—primarily within European manufacturing and agri-food sectors. While some studies adopt frameworks like the Resource-Based View or sustainability metrics, many lack explicit theoretical grounding. Key challenges identified include resource limitations, digital skill shortages, and regulatory uncertainty. This review highlights the need for more robust, theory- driven, and context-sensitive research, particularly across underrepresented sectors and regions. Its insights hold practical value for policymakers designing targeted CE interventions and for SMEs aiming to align innovation with sustainability goals