This paper analyses the role of consultancy services in the transition towards a Circular Economy (CE). To this aim, the paper brings together two different strands, the emergence of a new Circular Economy paradigm as a complex innovation process which faces many barriers and the innovative role of Knowledge Intensive Business Services (KIBS). Among KIBS, consultancy services are widely recognized in the field of innovation systems as a necessary agent for the adoption and diffusion of innovation by other agents. Circular-Oriented Innovation (COI) involves major changes, sometimes including new technologies and in most cases requiring the reorganization of value chains and the collaboration of different actors. This paper conducts a qualitative research focused on CE-related consultancy services provided by four pioneering companies in Spain. The paper sheds light on the functions developed by consultancy firms and discusses the main drivers and barriers towards COI. The findings suggest that KIBS may play an important role in the dissemination of the CE paradigm. Firstly, providing and managing knowledge to promote COI in their client's companies; secondly, through the strategic formation of networks and alliances with other key stakeholders, which are key for the practical implementation of CE; and finally, by disseminating the ideas and principles of the CE in the system and across the society. By means of their functions, we conclude that consultancy services may help to lower some of the barriers that are usually addressed by companies, and that revolve around the lack of knowledge and the associated uncertainty.