The aim of this study was to understand the use of complementary and alternative medicine (CAM) in cancer patients in Japan. This study was part of the Japan Hospice and Palliative care Evaluation 2016 (J-HOPE2016) Study. A multicenter questionnaire survey was conducted on a sample of bereaved family members of cancer patients who died at palliative care units. Data suggest that 54% of cancer patients use CAM. In comparison with a previous study in 2005 in Japan, categories of CAM vary widely; CAM previously included supplements mostly, but now exercise and mind and body therapy are also used. Most cancer patients use CAM without any harmful influence on their household economy and cancer treatment; however, in some patients, CAM incurs a large expense and a delay in starting cancer treatment. Therefore, it is important for medical staff and patients to have an opportunity to discuss CAM use. Multiple logistic regression analysis shows that CAM use is significantly associated with younger patients and highly educated families; moreover, there is a possibility that family members who use CAM have a high level of psychological distress. We must pay attention to the physical and the psychological aspects of cancer patients who use CAM and their families. Further studies are needed to investigate the use of each category of CAM, and to understand patients who use CAM and who die at home or in hospitals other than palliative care units.