This paper asserts that the changes India is experiencing on its demographic fronts have opened a window of opportunity for economic evolution, though they will also give birth to certain challenges at the same time which the country needs to address in time in order to harness the potential benefits of these changes. The paper takes into consideration the inter-state disparities with respect to preparedness of the bigger States of the country to deal with their changing working-age population as the demographic window of opportunity has been closed in the states of Kerala and Tamil Nadu, is about to close in the states of Delhi, Andhra Pradesh (including Telangana), Gujarat, Punjab, West Bengal, Karnataka, Odisha, Himachal Pradesh, Maharashtra, Jammu & Kashmir, Assam, Uttarakhand and Haryana while is completely open in the states of Chattisgarh, Jharkhand, Madhya Pradesh, Rajasthan, Uttar Pradesh and Bihar. The study is based on explanatory research design for a period of 30 years taken for seven points of time – 1990-91, 1995- 96, 2000-01, 2005-06, 2010-11, 2015-16 and 2020-21. The growth of NSDPPC is taken as the dependent variable and the independent variables include initial NSDPPC, initial working-age population, growth of working-age population, gross fixed capital formation, growth of gross fixed capital formation, total fertility rate, sex ratio, gross enrolment ratio and infant mortality rate. The study mainly focused to carry a detailed analysis of change in share of working-age population in total population on economic growth rate of selected Indian states. The results suggest that the magnitude of relationship between independent variable and dependent variables is changing across models while their direction remains same. Additionally, the paper studies in detail the favorable and non-favorable circumstances India is likely to experience to a certain extent because of its distinguished process of demographic transition.