To facilitate the understanding and implementation of circular design and eco-design in the molds and plastics sector, this guideline outlines fundamental principles of the circular economy and emphasizes the importance of Circular Design and Eco-design practices in promoting sustainability. It explores various circular business models and design strategies that optimize resource usage while reducing environmental impact. Additionally, the guideline presents case studies that illustrate successful implementation of these practices in real-world scenarios. Practical guidelines for enhancing energy efficiency, selecting sustainable materials, minimizing packaging, managing waste, and implementing closed-loop systems are also included to support the mold and plastics industry in transitioning towards a more sustainable future. By following these directions, companies can effectively adopt circular design principles and contribute to a more sustainable environment.