BACKGROUND: The relationship between advance care planning and religious beliefs, which are important for palliative care, is controversial in Western countries and has not been verified in Asian countries. AIM: To investigate the association between advance care planning discussions and religious beliefs in Japan. DESIGN: A nationwide survey conducted in 2016 using a quota sampling method to obtain a representative sample of Japan's general population. SETTING/PARTICIPANTS: We analyzed responses from 3167 adults aged 20-84 years (mean age ± standard deviation, 50.9 ± 16.8 years). The outcome was measured by asking whether the respondents had ever discussed advance care planning, and the main exposure by whether they had any religious beliefs or affiliations, and if so, their degree of devoutness. We analyzed religious beliefs, affiliations, and devoutness in relation to the occurrence of discussions using multivariable logistic regression models adjusted for possible sociodemographic covariates. RESULTS: Compared with respondents without, those with religious beliefs had significantly higher odds of having had discussions (adjusted odds ratio: 1.45, 95% confidence interval: 1.22-1.73). The devoutness of religious belief was proportional to the propensity of the occurrence of discussions (p for trend < 0.001). In addition, Buddhists and Christians had higher odds of having had discussions than did nonbelievers. CONCLUSION: The results suggest that holding religious beliefs, especially in Japanese Buddhism and Christianity, facilitates advance care planning discussions among Japanese adults, and thus, may help health-care providers identify those prioritized for facilitating engagement in advance care planning, especially in palliative and spiritual care settings.