Indo-US relations during the 21st century considered as an important and most significant in the strategic and security concern for both the countries. It is said that, despite their differences, foreign policies the healthy and positive relations between India and the US was started during the Regan administration. In 1991, India’s adoption of liberal policies on the economic sectors also an important landmark of their partnership. However, during the last decade of the 20th century Clinton Administration played an important role to continue their relationship. With the beginning of the 21st century under Bush administration Indo-US relations reached a level high specially security and strategic concerns. Since, September11 terrorist attack on the World Trade Centre, American declaration of global war on terrorism with the unconditional support of India changed their strategic policies especially defence and security ties. President George W. Bush changed the American decade old polices, by entering India into a strategic partnership. In this research paper focuses Indo-US defence and security relations during the Bush administration. It included joint military exercises, dual use of technology transfers, missile defence and bilateral defence trade between the two countries during the said period. Keywords: Indo-US defence, strategic and security concern, foreign policies, global war, strategic policies, security relations.