Objective: To evaluate the feasibility, acceptability, and effects of family-centered advance care planning (ACP) in patients with breast cancer. Methods: In this randomized controlled trial, 80 breast cancer patients were assigned to either a family-centered ACP group or a standard care group. Outcomes were measured at baseline and one month after the intervention using the Advance Care Planning Acceptance Questionnaire (ACPQ), Templer Death Anxiety Scale (T-DAS), Functional Assessment of Cancer Therapy – Breast (FACT-B), and a self-designed questionnaire. Results: Compared to controls, the intervention group showed higher ACP acceptance and improved quality of life (excluding physical well-being and additional concerns), along with lower death anxiety and reduced preference for life-sustaining treatments and aggressive end-of-life care. Conclusion: Family-centered ACP is feasible and acceptable for breast cancer patients. It enhances ACP engagement, improves quality of life, and reduces death anxiety. This study was prospectively registered in a publicly accessible clinical trial registry.