The article considers the development of strategic diagnostics of an enterprise in the condition of adaptation to a circular economy. In the context of global economic and environmental changes, strategic diagnostics is an important tool for assessing the effectiveness of the implemented changes and adapting to new challenges. The authors emphasize the importance of implementing the principles of a circular economy, which involve minimizing waste and reusing resources. It is obvious that in the process of adapting an enterprise to the conditions of a circular economy, strategic diagnostics plays an important role, which allows assessing the enterprise readiness to transition to a new economic model, determining its competitive advantages and developing effective development strategies. A set of strategic diagnostics tools with their adaptation to the conditions of a circular economy is systematized. It is substantiated that the proposed tools allow enterprises to effectively adapt to the conditions of a circular economy, reduce environmental impact, increase competitiveness, and find new opportunities for sustainable economic development. An algorithm for using strategic diagnostics of the enterprise in the context of adaptation to circular economy is developed. The presented algorithm allows enterprises to effectively adapt to the conditions of the circular economy, increase competitiveness, and ensure long-term business sustainability.