Objective We investigated family caregivers' awareness of disease status and attitude toward disclosure of disease progression compared with those of cancer patients and explored the potential association between family caregivers' attitudes and patients' quality of life (QOL). Methods We carried out a survey using self‐administered questionnaires answered by pairs of family caregivers and patients diagnosed with advanced cancer (n = 136 pairs). To assess patients' QOL, we used the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire. Results More than half of family caregivers (54%) did not have full knowledge of patients' advanced stage and goal of therapy. Positive attitudes toward disclosure were less common in family caregivers than in patients (59.4% and 85.4%, respectively; p < 0.01). The family caregivers' positive attitudes toward disclosure were inversely associated with patients' low functional scores (emotion [p = 0.04] and cognition [p = 0.02]) and high symptom scores (nausea and vomiting, pain, and insomnia; p < 0.05). However, in most QOL scales, patients' attitudes were not significantly associated with functioning and symptom scores. Conclusions A large portion of family caregivers may not know the patients' exact status. This study also suggests that the family caregivers' attitudes may differ from patients' and may be associated with patients' QOL. Copyright © 2014 John Wiley & Sons, Ltd.