Objective To describe the lived experience of decision fatigue among surrogate decision makers of ICU patients, and to provide reference for medical staff to implement decision assistance. Methods A purposive sample of 12 surrogate decision makers of ICU patients received semi-structured interviews, and data were analyzed using the Colaizzi analysis method. Results Five themes emerged: limited decision-making ability, increased negative emotions, difficulties in decision-making process, conflicts in decision-making process and insufficient decision-making support resources. Conclusion Surrogate decision makers of ICU patients experience decision fatigue. Medical staff should take interventions to promote the implementation of decision support and shared decision-making, resulting in improving decision quality and patient outcomes.