Japanese society has changed from the past as a result of modernization. However, there is one aspect of social action that has persisted at least in spirit. The purpose of the article is to show how traditional mutual help remains important, has been transformed in the transition to modernity, and has contributed to the continuing development of Japanese society. Mutual help can be divided into three types: yui, reciprocity through exchanging labor; moyai, redistribution based on a common store of goods and resources; and tetsudai, nonreciprocal support in social rites of passage. While these customs have almost disappeared from modern life, the tradition of mutual help is still manifest in some modern civic activities. The social system of mutual help arose from indigenous conditions in order to overcome the “tragedy of the commons.” Modern society might do well to reconsider such mutual help networks in search of ways of solving both public and private social problems in Japan and overseas as well.