Part of the European Green Deal is the Circular Economy Action Plan. Among other things, this plan formulates priorities for the design of products and production processes so that they are climate-neutral, correspond to a resource-efficient and circular economy (CE) and lead to a reduction of waste. These actions require companies not only to make changes to their organisational and management systems, but also to make investments. For this reason, these changes do not encourage companies to introduce the principles of the circular economy. Such encouragement can come from the business ecosystem. The aim of this article is to answer the question of whether companies gain such knowledge about the ecosystem in which they operate that encourages them to replace harmful technologies with friendly ones, to use their waste in their own production processes and those of other companies, and to neutralise their waste. This includes knowledge relating to the regulatory, economic, social, environmental and technological segments, as well as knowledge gained from buyers, suppliers and also competitors. The research hypothesis of the paper is that the greater this knowledge is, the more companies engage in the introduction of CE principles. In order to verify this hypothesis, an empirical study was conducted in 150 medium and large-sized companies belonging to 19 industrial sectors. Data were obtained using an interview questionnaire and were processed using a Kruskal-Wallis ANOVA and post hoc test. The results obtained allow us to conclude that knowledge of changes occurring in macro-environmental segments is more influential than knowledge obtained from buyers, suppliers and competitors. Companies that have knowledge of the changes taking place in the ecosystem perceive and exploit these changes and actions towards a circular economy as business opportunities. The research results obtained are useful for indicating the practical steps that leaders in the introduction of circular economy principles are taking in order to acquire the necessary knowledge about the ecosystem. They can also provide some contribution to the development of a sustainable product policy legislative initiative by the European Commission using the performance of these leaders.