This study investigates the relationship between religiosity and volunteering in Japan. Previous research has shown that people who belong to religious affiliations and who attend religious institutions regularly tend to volunteer. However, little is known about whether religiosity facilitates volunteering among those Japanese not involved in religious groups, and which dimensions of religiosity have apositive influence on such activity. Therefore, this paper, employing data from representative national Japanese samples, examines the influence of dimensions of religiosity on volunteering among Japanese without religious attachments.
 The study finds that while both collective religiosity (religious affiliation and attendance) and diffused religiosity (prayer and belief in guardianship) predict volunteering among the Japanese, only diffused religiosity is related to volunteering among non-members of religious denominations.
 The finding indicates that volunteering among the latter group is promoted by religiosity, particularly diffused religiosity. The result that private prayer and individual religious belief or experience promote volunteering is in line with recent research in Western countries. Meanwhile, a direct relationship between religious attendance and volunteering among those who are not attached to religious denominations has not been shown. This suggests that Japanese temples, shrines, and churches do not directly foster volunteering by forming networks of people, but that they indirectly promote it by enriching the piety that has been culturally diffused in the community.