Although informed consent is rooted in the growing affirmation of the subject’s autonomy, medical anthropology has highlighted the inherent limits of this procedural notion. My ethnographic research in neurological and geriatric clinics between France and Italy showed the triangular (dis)trust relationship—between older people with Alzheimer’s disease (AD), their doctor, and their caregiver. Following their cognitive decline and loss of autonomy, people with Alzheimer’s disease (AD) could be victims of epistemic injustice in two specific moments of the illness: the diagnostic disclosure and the institution of legal protection. If the diagnostic information diminishes the patient’s credibility, the institution of legal protection undermines the patient’s social identity and legal status. However, when caregivers preserve an unconditional trust in the permanence of the patient’s subjective identity, this trust may be conveyed to clinical teams, significantly improving the therapeutic relationship, the course of the disease, and the quality of life for all the actors involved.