Objective Previous research suggests that spirituality/religiosity has benefits for both mental and physical health, measured using biological indices such as cortisol and IL‐6. However, there have been few studies concerning the association of religious beliefs with oxytocin, a neuropeptide hormone secreted by the pituitary. Levels of peripheral oxytocin are thought to reflect the strength of bonding and stress regulation in social relationships. As such, the oxytocin system may underpin the biological mechanisms by which belief in life after death is associated with good mental and physical health. Here, we examine associations between oxytocin and belief in life after death. Methods We recruited 317 community‐dwelling people, aged 65 or older, without cognitive or mental deficits, and living in rural Japan. We recorded demographics, belief in life after death, and logical memory using the Wechsler Memory Scale. Levels of serum oxytocin were obtained using an enzyme immunoassay method. Results Serum oxytocin levels were higher among women than men and were negatively associated with strength of belief in life after death. Conclusions Our findings could be interpreted differently depending on whether the anxiogenic or anxiolytic function of the oxytocin system is considered. Greater endorsement of afterlife beliefs may reduce secure attachment. Alternatively, based on the literature suggesting that basal levels of oxytocin are lower in those with reduced relational distress or anxiety, afterlife beliefs may play a role in these reductions. Copyright © 2016 John Wiley & Sons, Ltd.