Purpose <p>Advance directives (AD) are a key tool within advance care planning (ACP), intended to support patient autonomy and guide end-of-life care. Despite their legal recognition in France, their use in the general population remains limited. Moreover, data on AD use among patients with advanced cancer, a population particularly concerned by end-of-life decisions, remain scarce. This study aimed to assess the knowledge and opinions regarding AD among patients with advanced cancer in France who were receiving specialized palliative care.</p> Methods <p>Between 2016 and 2020, we conducted a multicenter cross-sectional study across 14 palliative care departments in France. Patients with advanced cancer completed a standardized questionnaire assessing their awareness, use, and perceptions of AD, along with sociodemographic and clinical characteristics.</p> Results <p>A total of 331 patients were included. Among them, 53.5% were aware of AD, and 23.6% had completed one. Overall, 72.2% of patients supported legally binding AD, and 66% opposed fixed expiration dates; among those favoring time limits, most chose 1–3&#xa0;years. In multivariable analysis, a higher educational level and prior treatment during the curable phase were independently associated with knowledge of AD, while completion was associated with older age, higher education, and the absence of ongoing cancer treatment. A higher educational level was also associated with favoring legally binding AD.</p> Conclusion <p>French rates of AD completion remain modest. Our findings highlight the need for personalized, repeated discussions about end-of-life preferences and for enhanced clinician training in ACP. AD should be approached as a flexible tool within broader patient-centered discussions.</p> Clinical trials identifier <p>NCT03664856.</p>