This article analyzes the reasons of the differences in US foreign policy towards nuclear development in India and Iran. The purpose of this study is to find out the reasons for the different policies issued by the United States towards nuclear development in India and Iran. The United States as the "leader" of the world nuclear regime plays a role in providing "validation" for other countries which are allowed to develop nuclear technology. But there was a different attitude towards nuclear development in India and Iran. This article uses the concept of National Interest and Security Dilemma to find out the reasons behind the policy. The conclusion is that there is a shift in the interests of the United States and changes in political dynamics in India and Iran and the countries around the two countries.