In recent times security is being interpreted increasingly as comprehensive security, the focus has been shifted towards the human security, the economic security as well as environmental security. As defined by the United Nation's Human Development Report of 1994, human security includes safety from chronic threats and harmful disruptions in the patterns of daily life. In the growing literature, the concept of human security has been expanded to include economic, health and environmental concerns for energy security become important. India is among the top four consumers of energy just behind the U.S., China and Japan, India's total primary energy demand in 1997-98 was 25.5 million tons and this is expected to rise up to the 770 million tons in 2020. Currently the share of fuels in primary energy dominated by coal and oil. India cannot meet this demand domestically and has to rely on outside supplies. This creates a situation of dependence and call forCooperation from other nations-states. Currently energy resources such as coal and oil are becoming extremely depleted and will run out in the near future. The best replacement is the nuclear energy. It is the fastest growing power generation industries in the world, with this regard it is the safest, cleanest and most efficient. Today 15 percent of the world's electricity comes from nuclear power. As for the India's nuclear energy is concerned it is the fourth largest source of electricity. This industry is expected to undergo a significant expansion in the coming years by passing the Indo- US nuclear deal, and then India is expected to generate an additional 25,000mw of nuclear power by 2020. There has always been acute awareness of the fact that some of the materials technologies and expertise that are relevant for peaceful use of nuclear energy can be used equally for making nuclear weapons. India conduct a nuclear test in 1974 partly in response of external challenges, however, it claimed that the detonation was a peaceful explosion. India did not declare itself to be a nuclear power until it conducted a seemed series of nuclear test in 1998. India also did not sign on NPT and CTBT also due to its external challenges from various countries. Through this reason India facieses number of sanctions many of which were lifted by late 2000 A.D. The purpose of the (Indo-US Nuclear Deal) agreement is to enable full civil nuclear and energy cooperation between the India and the United States. The agreement provides full civil nuclear energy cooperation covering nuclear reactors and aspects of the associated nuclear fuel cycle including enrichment and reprocessing. This agreement also opens the doors for cooperation in civil nuclear energy with other countries. This agreement provides for the application of IAEA safeguards to transferred material and equipment. The present study contains six chapters. The first chapter shows the concept of comprehensive security and also highlights different aspects of security. The second chapter deals with energy security that plays an important role in state security. The third chapter deals with India's Energy Scenario and Politics which shows its various related issues. The fourth chapter deals with Nuclear energy and nuclear proliferation, it shows that how nuclear energy is also used for weapons also. The fifth chapter deals with Indo- US nuclear deal and its role in enhancing India's energy security, through which India can use nuclear energy in peaceful purposes. The sixth and the last chapter deals with assessment of indo-us nuclear deal (123 agreement) in different aspects.