ContextThe Bereaved Family Survey is an important method for evaluating the quality of palliative care. ObjectivesTo examine the distress and benefits of bereaved families of patients with or without cancer, who participated in a Bereaved Family Survey, and identify factors associated with distress and benefits. MethodsWe conducted a nationwide cross-sectional, self-reported questionnaire mail survey among the bereaved families of patients who died of cancer, heart disease, cerebrovascular disease, pneumonia, or kidney failure. Participants answered questions on a four-point Likert scale measuring the distress and benefit associated with participating in the Bereaved Family Survey. We conducted a qualitative analysis of responses to open-ended questions about the distress and benefits of participating in the survey to comprehensively examine the distress and benefits of participating in the survey. ResultsQuestionnaires were distributed to 115,816 eligible bereaved family members between February 2019 and February 2020; 62,576 (54.0%) family members returned valid responses. Distress and benefits accounted for 51.4% and 49.3%, respectively. The results of the binomial logistic analysis for distress were significantly higher among cancer patients (p<0.001–0.003), 20–39-year-old patients (p<0.001), female bereaved family members (p<0.001), and bereaved family members with poor mental health statuses (p<0.001). Factors related to “benefit” were significantly higher among over-80-year-old bereaved family members (p<0.001), higher care evaluation scale (CES) scores (p<0.001), and higher good death inventory (GDI) scores (p<0.001). ConclusionBereaved family members experience both distress and benefits. There is need to devise ways to reduce distress and increase its benefits to continue assessing the quality of palliative care.