The social sector is one of the most important sectors of any economy. The level of development of this sector directly affects the level of human development of a region or a country. However, the social sector can play an important role in affecting the rate of economic growth as well. As the development of the social sector starts, quality of life will improve, leading to quality human capital that leads to higher labour and other factor productivity. Keeping these things in mind, this research paper discusses the social sector expenditure of Bihar from 1980-81 to 2017-18. This paper investigates, does the adaptation of Millennium Development Goals (MDGs) affect the allocation of social sector and what is the status of four critical expenditure ratio suggested by UNDP in the state? The study find that the allocation of social sector expenditure has been increasing constantly but out of four important social sector expenditure ratios suggested by UNDP, only the social priority ratio is well above the recommended expenditure norms.