The current global climate crisis demands an immediate shift towards new business models that operate in circular and non-linear logic. However, despite discussions about this transition from the late 1960s, achieving a circular economy remains lengthy and challenging. Manufacturing companies must acquire and develop new skills and expertise to implement this change successfully. Additionally, they must continually analyze and evaluate their performance from multiple perspectives over an extended period to obtain optimal results. The main objective of this research is to delve into the approaches and tactics utilized by four companies based in Italy, representing manufacturing realities, including circular models in their portfolio diversification strategy. The research theorized this model as “Circular Diversification” (CD), and the study seeks to analyze how these companies have implemented it in practice, placing particular emphasis on the role of Design, actual or presumed, by going to find out which Design professions play a crucial role in CD. The research uses qualitative case-based reasoning methods to extrapolate meta-knowledge; Issue-Concept-Form (ICF) is the semantic model chosen to break down information from case studies. Next, three parameters are crossed through an Alluvial Diagram to show intersections: problem/motivation (former Issues), strategy (former Concept), and form/solution (former Form), which Designers adopt are identified. Three relevant Design figures operating for a Circular Diversification are determined from the intersections: Systemic-Circular Designer, Product Designer, and Strategic Designer. Specific forms/solutions can be replicable and scalable recommendations in other manufacturing and territorial contexts, paving the way toward a Circular Diversification support service.