Rare diseases are characterized by a wide diversity of signs and symptoms and vary not only from disease to disease but also from person to person, and living with a disease leads patients to peculiar experiences, without limits of time and space, as they extend to various environments and relationships of their lives. Therefore, the objective of this study is the theoretical interaction between value co-creation (VC) and the stakeholder theory (ST) with the shared decision-making (SDM) health care theory, to enable the analysis of the relationships between patients and their stakeholders in the co-creation of value for decision-making focused on the patient’s quality of life. It is configured as a multi-paradigmatic proposal by enabling the analysis of multiple perspectives of different stakeholders in health care. Thus, co-created decision-making (CDM) emerges with emphasis on interactivity of the relationships. As previous studies have already highlighted the importance of holistic care, seeing the patient as a whole and not just the body, studies with CDM will be beneficial for analyses that go beyond the clinical office and doctor–patient relationships, extending to all environments and interactions that add value to the patient’s treatment. It was concluded that the essence of this new theory proposed here is neither in patient-centered care nor in patient self-care, but in co-created relationships with and between stakeholders, including non-health care environments that are important to the patient, such as relationships with friends, family, other patients with the same disease, social media, public policies, and the practice of pleasurable activities.