The present article is based on research into the process of working-class formation in Rio de Janeiro in the period between the end of the nineteenth century and the early years of the twentieth. It explores the significant shared experiences of workers subjected to slavery and “free” workers in the process of working-class formation, and aims to demonstrate that the history of that process in Brazil began while slavery still existed, and that through shared work and life experience in Rio de Janeiro, as in other Brazilian cities where slavery was strong during the nineteenth century, enslaved and “free” workers shared forms of organization and struggle, founding common values and expectations that were to have a central importance in later periods of class formation.