This article examines the labour renewal strategies implemented by Central de Los Trabajadores de la Argentina. It argues that union organizing is conditioned by historical legacies and structural constraints, while social movement unionism, which for the most part promotes building alliances with community groups, can be achieved by taking advantage of political opportunities and mobilizing resources. To maintain these alliances, trade unions and social movement organizations need to build institutionalized partnerships and compensate for their individual weaknesses. The article also argues that organizing the unorganized and building alliances with the community are not a substitute for each other. It is also argued that labour's power derived from its location in the economic system still stands as an essential source of labour renewal.