The scope of this dissertation is to demonstrate how the concepts of choice architecture and nudge, seen through the lens of libertarian paternalism, can be compatible with civil-constitutional law and used as an instrument for the promotion of well-being in various aspects of life. For this purpose, assumptions about decision-making shall be fixed as a base for libertarian paternalism. First, as a theoretical foundation, we discuss the findings of studies by Daniel Kahneman and Amos Tversky about bounded rationality to prove that people are not entirely as rational as they might think and make predictable and systematic errors of judgment. At that point, we will work on the heuristic principles and cognitive biases to prove the concept of bounded rationality. Then, with these assumptions fixed, we shall present Richard Thaler and Cass Sunstein s concept of Libertarian Paternalism, choice architecture, and nudge. Next, the filters of legitimacy surrounding interventions in the choice architecture shall be discussed, focusing on those developed by Cass R. Sunstein and Lucia A. Reisch, aiming to bring such filters in line with the civil-constitutional reality. Finally, this thesis will demonstrate that the Brazilian legislator, even without the current theoretical framework of cognitive sciences, reconciles the concepts of bounded rationality and choice architecture and uses various instruments which could understand within the Paternalist Libertarian context.