Social capital is the fourth pillar of sustainable development. Whereas natural, physical and human capital constitute the “wealth of the nations”, it is social capital that contributes to harmonious growth. Using the framework of New Institutional Economics, both social capital and sustainable development are explored by their casual impact on informal institutions. Values, habits and beliefs which define social cohesion and impact future generations are the source of continuous development and therefore implicate the egalitarian redistribution of wealth. By taking into consideration the growing number of research in the aforementioned fields of study, this article hopes to introduce a potential research programme where social capital is the main source of sustainable development. The article also seeks to point out the importance of preserving other forms of capital.