The history of the North Atlantic Treaty Organization (NATO) will say that the first, and so far only, time NATO has called upon its Article 5 collective defense clause was on September 12, 2001, following a terrorist attack on one of its members. Yet, until the agreement by NATO Heads of State and Government on the new policy guidelines on counterterrorism on May 20, 2012, NATO did not have an agreed policy to define its role and mandate in countering terrorism. In the 11 years that have followed the 9/11 attacks on the United States, NATO has opted for a pragmatic approach to the fight against terrorism and succeeded in identifying its added value. The result has been a series of substantial counterterrorism activities. Their impact, however, has been mitigated by the lack of an agreed policy defining NATO’s rightful place among international counterterrorism actors. The evolving nature of the terrorist environment and of the global responses required has made it necessary to reassess the threat posed by terrorism and its implications for the Alliance. The new NATO policy guidelines on counterterrorism are the result of a comprehensive intellectual and political process that started with the 2010 Strategic Concept and led to the conclusion that in an era in which emerging challenges blend collective defense with the broader concept of collective security, the lens of collective interest must replace the prism of national perspectives. With this in mind, the overall judgment on the new policy guidelines can and should be positive.