Methods: In two phases, the aims of this study are to (1) design and tailor the intervention, and (2) implement and evaluate it. In the first phase, theory and user-centred design will be used to tailor a multifaceted intervention comprising a distance professional training program on shared decision making, and five shared decision-making tools dealing with difficult decisions often faced by seniors with dementia and their caregivers. Each tool will be designed in two versions, one for clinicians, and one for patients/caregivers. Forty-nine clinicians and 27 patients/caregivers will be invited to participate to three cycles of design-evaluation-feedback of each intervention components. Besides think-aloud and interview approaches, they will also complete questionnaires to identify the factors most likely to influence their adoption of shared decision making after exposure to the intervention. Thereafter, the intervention will be modified by adding/enhancing behaviour-change techniques targeting these factors. In the second phase, the effectiveness of this tailored intervention will be evaluated before/after implementation, in a two-armed, clustered randomized trial with a three-month follow-up. A convenience sample of 6 primary care clinics will be enrolled in the province of Quebec (Canada), and clinicians who practice there will be recruited (mostly family physicians, nurses, and social workers). These clinics will then be randomized to immediate exposure to the intervention, or usual care with delayed exposure to the intervention. Overall, 180 seniors with dementia, their caregivers, and their healthcare providers will be recruited. The investigators will evaluate impact of the intervention on patient involvement in the decision making process, decisional comfort, patient and caregiver personal empowerment in relation to their own health care, patient quality of life, caregiver burden, and decisional regret.