This research develops a methodological a perspective to evaluate the impact of conditional cash transfer programs, due to the need to broaden the understanding of social change and identify, describe and explain the social effects in the medium and long term. For this, the impact evaluation of social programs and traditionally used methodologies are examined and an onto-epistemological change is proposed to linked to critical realism, understanding that this contributes to deepen the study of the "social". Three approaches are proposed from this philosophical school: theory-based approaches, realistic evaluation and analysis of the contribution.