Do-not-resuscitate (DNR, meaning not to perform cardiopulmonary resuscitation), implies reducing ineffective aggressive medical treatments when a patient is near the end of life, allowing patients to pass away in a peaceful and dignified way. Moreover, it appears to be a common phenomenon and challenge for children to become surrogates to authorize DNR for their parents. In Chinese-speaking culture, it is often expected that the eldest son assumes the role as a primary decision-maker. The purpose of this study was to investigate the decision-making process and emotional experiences of an eldest son serving as a surrogate decision-maker for his father in signing a DNR consent form. Additionally, it aimed to shed light on the impact and transformation of the eldest son’s role in this process. This study employed qualitative research. A single research participant was recruited through purposive and convenience sampling for participation. A semi-structured interview was conducted, and the interview data were analyzed using thematic analysis. The study identified four key themes in the experiences of the participant’s signing DNRs: (1) Why me?; (2) The influence of ’filial piety’ in decision-making; (3) Relatives’ incomprehension and cognitive swing — the contradictory experience of signing DNR as an agent; (4) So it is me who signed — The role of medical training background and sibling support in decision-making. The study also found two themes regarding the transformation of the eldest son’s role during the bereavement process: (1) The eldest son was the only one suffering from the burden of seeing and being aware of the dilemma; (2) The eldest son adopted the modern cultural perspective to involve his younger siblings to share the responsibility in the decision-making process. The study concluded as follows: the process of signing a DNR as a surrogate involved complex emotional experiences, including anticipatory feelings of loss and ambivalence. Medical decision-making regarding DNR often led to conflicts between traditional filial piety concepts and modern ethical considerations. The research participant, influenced by his medical training background and reciprocal filial piety, made his DNR decisions based on assessments of personal needs and family well-being. This approach aligned with the adaptive strategies employed by the eldest sons to navigate the traditional and modern filial piety dilemmas. Considering these findings, the study offers several suggestions for future research and mental health practitioners.