Improve resource efficiency through circular economy is one of the key element of the EU Green Deal. Besides being beneficial for the reduction of raw materials supply, moving towards a circular economy will parallelly contribute to reach important objectives of the EU Green Deal, such as the reduction of greenhouse gas emissions and the decrease of environmental pollution. Industrial symbiosis allows to implement the concept of circular economy in specific territorial contexts. This paper briefly describes the methodological approach and the tools developed and tested by the Italian National Agency for New Technologies Energy and Sustainable Economic Development (ENEA) to support small and medium enterprises to improve their resources efficiency. This approach includes the resource audit and the methodology for the definition of industrial symbiosis networks and it is structured in four steps: data collection, identification of possible valorisation options for resources either internally to the company or externally though industrial symbiosis, the analysis of potential benefits and barriers, and the preparation of a summary report.