It was not until the September 11, 2001 terrorist attacks to the twin towers in New York and Pentagon in Washington that NATO was concerned about terrorism as a threat to the security of the Alliance. No matter how agile the response to the 9/11 terrorist attacks was, NATO has confronted a lot of gaps to work on defense against terrorism (DAT). Since then, starting with the 2002 Prague Summit, NATO has taken important steps to transform itself to adapt to the new security environment as well as establishing a DAT policy. Although important gains have been made towards setting a vision, implementing such vision has a considerable way to go, let alone achieve success. Within this framework, the article seeks to explain the evolution of NATO's stance towards terrorism in the post-Cold War era, the milestones in the development of NATO's DAT policy, its military concept for DAT and its operations and joint efforts related to DAT.