This study provides an examination of the relationship between circular economy (CE) practices and firm performance in small and medium-sized enterprises (SMEs) in Europe, following a multi-level approach. The research project outlines the stages involved to reach this goal. The first stage (paper 1) examines the trends in the existing research. We verified the variables used, the type of data, the method of analysis, the type of industry, the size of the company, the size of the sample and the topic to which the article belongs. The results indicate that there is no clear consensus on the best way to measure and operationalize CE practices and firm performance, however the variables identified can be used as a guide for future research on CE and firm performance. The second stage (paper 2) we investigate how the economic, social, and environmental performance indicators of the SME country moderates the relationship between CE practices and firm performance. In summary, the results support that the financial impact of adopting CE is positive, and it is affected by the level of national economic and environmental performance. The third stage (paper 3) the aim is develop and test empirical model include moderation by meso-level. We examined the function of intermediaries in involving SMEs in CE activities, and how the presence of Industrial Symbiosis Networks (ISN) affects SMEs performance. The findings affirm that ISNs can boost CE adoption and intermediaries can assist SMEs in surmounting CE obstacles.