In this study, we test whether Putnam’s general claim of a negative effect of ethnic diversity holds for (active and passive) involvement in three types of voluntary organizations: leisure, interest, and activist organizations. Using data from the European Social Survey (wave 1), we applied multilevel analyses distinguishing individuals, regions, and countries. Only at the regional level, did we find that ethnic diversity reduced involvement in interest organizations. Yet, ethnic diversity induced passive involvement in activist organizations. Subsequently, we included mechanisms derived from conflict and contact theory to disentangle the indirect effects of ethnic diversity. Ethnic threat perceptions influenced participation in all voluntary associations negatively, while intergroup contact turned out to have positive influences. Our findings stress the necessity of distinguishing different types of voluntary organizations and modes of involvement and underline the importance of incorporating indirect effects of ethnic diversity.