Objectives: This study aimed to describe the experiences of bereaved family members of cancer patients in terms of regret in relation to ending terminal treatment for the patient. Methods: We conducted a semi-structured qualitative interview of 37 bereaved family members regarding their decision-making and their psychological adjustment from the time they made the decision to terminate treatment. Interviews were analyzed using qualitative content analysis. Results: Approximately 40% of bereaved family members reported that they had some regrets about their decision. Regret contents were classified into 8 categories and diversified from 4 categories at the time of decision-making to 7 categories after the death. The reasons for regret were classified into 43 categories. Common factors that minimized regret included situations at the time when they made the decision, such as patient- and family-specific factors and relationship with the medical staff. In comparison, the common reasons for regret centered on factors related to the approach for decision-making, such as the process, options, as well as psychological coping and relationships with medical staff. Conclusion: The results suggest that regret in the bereaved could be modified by understanding the relationship between regret characteristics and psychological coping.