As the family usually plays a central role at the end of life, the quality of family relationships may influence how individuals approach advance care planning (ACP). Our study investigates the associations of trust in relatives with regard to end-of-life (EOL) issues-used as a proxy measure of family relationship quality-with individuals' engagement in EOL discussions, advance directive (AD) awareness, approval and completion, and designation of a healthcare proxy. Using nationally representative data of adults aged 55 years and over from wave 6 (2015) of the Survey of Health, Ageing, and Retirement in Europe (SHARE) in Switzerland (n = 1911), we show that complete trust in relatives is related to higher engagement in ACP. Subject to patient consent, the family should, therefore, be included in the ACP process, as such practice could enhance patient-centered EOL care and quality of life at the end of life.