This article is concerned with the analysis of features, dynamics and trends of the U.S.-EU cooperation in the fight against terrorism (2001-2021), which is one of the cooperation priorities in the security sphere, but at the same time is associated with a number of contradictions that complicate transatlantic relations. The article will consider not only the foreign policy aspects of the U.S.-EU cooperation in the fight against terrorism, but also less well-covered aspects of their relations, such as the specifics of the legal and regulatory framework for anti-terrorist cooperation, comparative analysis of strategies and the impact of the partners' internal approaches on the development of cooperation. A comprehensive study of the problems of cooperation between the EU and the U.S. in the fight against terrorism in the period 2001-2021 on the basis of foreign and national scientists' works will allow for an assessment of the development prospects for the transatlantic cooperation. The author came to a conclusion that the U.S.-EU international cooperation triggered by 9/11 terrorist attacks led to boosting the exchange of critical information, prevention of terrorist acts and development of military cooperation as well as to increased divisions among the partners. The U.S. aspirations to play the leading role in the fight against terrorism and its unilateral actions undermining the European sovereignty and sometimes contradicting principles constituting the base of their counterterrorist approaches are among the main controversies. However, despite the differences, transatlantic cooperation in the fight against terrorism remains important for the partners as it serves their core interests and is characterized by the common purposes and values, which should be taken into consideration in order to make conclusions for Russian foreign policy.