Although volunteers are becoming increasingly important for promoting social activities, many nonprofit and civil society organizations face a volunteer shortage, which limits their options of the activities. To identify an effective method for recruiting volunteers, we conducted a national survey in Japan using a web-based questionnaire, and analyzed the relationships between volunteering and leisure time, financial resources, and information sources that led to volunteering. There was no practical relationship found between the time spent volunteering and leisure time or financial resources, including the perceived net benefit of volunteering. Many individuals obtained information related to participating in volunteer activities from community sources or through personal contacts. Most information was obtained by coincidence rather than by active searching. These results indicated that individuals were more likely to initiate participation in volunteer activities by spontaneously responding to opportunities that arose rather than by making choices comparing the costs and benefits.