This research seeks to explain changes in labor relations, the emergence of new forms of employment and its effects on unionism in the period between 1975 and 2010 in Chile. This research take into account the changes in the world of work, especially the phenomenon of labor precariousness, and the trajectories and emerging union strategies in this process. In this current rant, between labor precariousness and organization of union actors (stakeholders), we seek to relate the transformation of the labor conditions and the union activity in Chile. We assert that there is an adaptive heterogeneity and limited diversification of union strategies in the context of labor precariousness in Chile, which is possible to prove and verify through the experience of union leaders from different companies and productive sectors of the country, and the tendencies in indicators and labor statistics. It is in this current tension between labor precarity and organization of union actors (stakeholders) that our principal research questions arise: How has the process of labor precarity modified, altered or rearranged union activity? Are new union strategies emerging in the context of labor precarity? Are we in a process of synchronization of labor precarity tendencies and the transformation of the world of work with new core problems for unions? In this study we assert that there is an adaptive heterogeneity and limited diversification of union strategies occurring in the context of labor precarity in Chile, which is possible to prove and verify based on the experience of union leaders from different companies and productive sectors of the country. Although a series of studies confirms the phenomenon of labor precarity in different contexts (such as productive sectors, occupations, gender, etc.), there is no research linking the transformation of working conditions, the regulatory framework, the occupational structure and impacts on the adjustments of union strategies in Chile. In order to contextualize this debate, in the first part of this research we analyze a theoretical construction of labor precariousness, from the Latin American experience, problematizing its emergency in a productive, spatial and temporary context, in relation to an industrialized Europe, where the discussion of labor precariousness originally emerges.