Shortcomings in manufacturing companies’ capabilities to execute circular economy business modelling have delayed a broader dissemination of circular business models beyond the stage of pilot projects in niche markets. Circular economy poses additional uncertainties for innovation that are not common for manufacturing companies’ traditional activities and business as usual. To cope with such challenges, they lack systematised practices and proactive advice, which are scant in available literature and approaches. The paper presents the development of the tool Circular Economy Business Modelling Expert System within manufacturing companies, intended to address these limitations. Based on systematised business modelling practices for circular economy and proactive advice on potential circular business model configurations, the expert system enhances strategic thinking for circular economy, supporting companies to come up with varied alternative business models with reasonable and viable value propositions to deploy circular benefits accordingly. The expert system was streamlined based on literature review, development, testing and evaluation with 12 practitioners from 10 companies. The paper discusses the main functionalities of the expert system and the results of its application into varied manufacturing companies. The application of the expert system has demonstrated to benefit companies with: inspiration for best practices on circular business modelling, a structured framework for confirming assumptions and a logic structure that prompts decision-making and reduces uncertainties.