Inequality and labour informality are still distinctive characteristics of Latin America. However, most of the countries have succeeded in reversing the upward trends in both informality and inequality in the 1990s. These positive dynamics have been noteworthy in Argentina and Brazil. This paper analyses the processes of labour formalization in these countries and its interrelation with the evolution of income inequality over the 2000s. It contributes to two current debates. The first one refers to the role of labour market flexibilization in employment formalization. The second one is related to the reduction of income inequality. Most of the literature places emphasis on the evolution of the returns to education. This paper complements this approach by analysing the contribution of formalization to the reduction of inequality in these countries.