Objectives Research has found that spirituality/religiosity has a salutary association with mental/physical health. However, the association of belief in life after death with well‐being has rarely been studied, and the same is true of its association with biological indices, such as monoamine transmitters. Therefore, we examined the associations between well‐being and religiosity, salivary 3‐methoxy‐4‐hydroxyphenylglycol (sMHPG), and demographic characteristics. Methods The participants were 346 community‐dwelling people, aged 65 years or older, without cognitive or mental deficits, in rural Japan. Measures of religiosity consisted of belief in life after death, attachment to life, and experiences related to death and religion. The measures were assessed by scales specifically suited for Japanese religious orientations. Participants' well‐being was assessed by a life satisfaction scale containing two subscales. We also measured sMHPG, a major metabolite of noradrenaline that is thought to reflect certain psychological states, such as psychomotor retardation and effortful attention. Results One subscale of life satisfaction was positively associated with belief in life after death and sMHPG, and the other life satisfaction subscale was positively associated with education and death/religion‐related experiences (e.g., visiting family graves or loss of a friend). Gender differences were found in afterlife beliefs and each life satisfaction subscale. Conclusions These results suggest that religiosity, including belief in life after death and death/religion‐related experiences, is salubriously associated with mental health among older people, especially women, living in rural Japan. The basal level of sMHPG was positively associated with life satisfaction, but not with belief in life after death. Copyright © 2014 John Wiley & Sons, Ltd.