The current linear economy focuses on a ‘take-make-use-dispose’ paradigm, prioritizing ‘volume-over-value’. Significant planning and experimentation are needed to understand how to develop new business models that are not only ‘circular’, but also desirable for people, technically feasible and financially viable. More insight is needed into the practices of business experimentation to accelerate the transition to a circular economy. We investigate the following: What types of experimentation practices do companies adopt in the transition to a circular business model? Our analysis is based on action research with over 40 organizations. Based on this, we provide an overview of business experimentation practices inside a diverse range of organizations and possible tools, approaches and lessons learned. Recommendations focus on the practices, process, environmental impact assessment, partnering and management of complexity in future tools and methods. We also propose a framework for circular business experimentation and future research directions.