Extant theories of member participation in unions have sought mainly to explain spot decisions to participate in collective action and therefore are limited in explaining how members can have an impact on union governance. This article conceptualizes life-long activism as informal careers that begin with politicizing life experiences, are nurtured through the fulfilment of organizational roles and develop by gaining status and skills both within the union and in the members’ community. Data are reported from the Los Angeles Justice for Janitors campaign two decades after initial mobilization occurred there. Existing literature has depicted activism as a response to calculus and stimulus rather than as a search for meaningful work. An alternative perspective is advanced where the force of a calling acts as the main driver of activism in which the union is seen as a vehicle for the pursuit of social justice.