Industrial symbiosis (IS) is a collaborative strategy where organisations share or exchange by-products, materials, energy or waste to address environmental degradation, resource depletion and sustainable productivity. Knowledge sharing, which can be supported by a facilitator, is commonly expected to enable exploration and assessment of potential exchanges during IS emergence. Drawing on a multi-case study of four IS networks in Europe during their emergence phase, this study explores how different facilitators support knowledge sharing. The study offers insights into distinct IS facilitator roles for knowledge sharing, including stewards, mediators, catalysts and moderators. The findings show that IS facilitator characteristics, such as the strategic relevance of IS developments to facilitators and facilitators' ownership of critical tangible resources, as well as network structures may influence their role. The paper concludes with theoretical and managerial implications that are relevant for those involved in IS facilitation and with suggestions for future research within the field.