The aim of this work is to investigate how egalitarian liberalism legitimises the implementation of affirmative action policies to tackle certain inequalities in society. To this end, John Rawls' Justice as Fairness is used as the central reference for the discussion of egalitarian liberalism and how it justifies the implementation of such policies. Rawls' theory of justice proposes the elaboration of principles of justice to evaluate the basic structure of society according to how it regulates the distribution of an appropriate level of primary goods, considered to be the means and social conditions necessary for the adequate development of each citizen. Bearing in mind that unequal access to and distribution of these goods jeopardises people's life expectancies, generating serious social and economic inequalities, affirmative action works as a mechanism of equity and social justice by rectifying some of these inequalities, guaranteeing real opportunities open to all on an equitable basis, including access to public office, social positions and quality education.