Two correlational studies of activists examined the association between belonging to community organizations or groups and sustained activism within a particular domain. In Study 1 (N = 45) larger activist networks, controlling for activist identification and greater political knowledge, were associated with stronger activism intentions. In Study 2 (N = 155), larger Time 1 peace activism social networks were associated with more Time 2 peace activism and, via Time 2 activism, with sustained activism at Time 3. In contrast, Time 1 nationalist and party political identities were inhibiting factors of peace activism at Time 2, and indirectly at Time 3. In addition, larger peace activism networks at Time 1 were associated with greater international human rights activism and Christian activism at Time 3, but not as consistently with other forms of cross-domain activism. The possible organizing principles for these interrelationships are discussed.