This article overviews the 30 years of experience of Lithuania, Estonia and Latvia in developing national systems of legal cooperation in criminal matters. In order to reveal individual experiences of the three States, the developments of law and practice of each State from the re-establishment of its independence to the present day are covered in separate sections of the article. For this purpose, experiences related to the development of national laws are presented over two time periods – before and after membership in the European Union. The experience of each State in concluding different international agreements on legal cooperation in criminal matters is also discussed. Considerable attention is paid to the implementation of the secondary legislation of the European Union, such as Council framework decisions and directives. Irrespective of the membership of the Baltic States in the European Union and the areas of freedom, security and justice developed in this area on the basis of the principle of mutual recognition, the system of cooperation with third countries retains its particular relevance and is also analysed in this article. In order to reveal the positive and negative experience of each State in this area after the re-establishment of independence, an analysis is conducted of both national and international legislative provisions. The article also highlights and explores the main transformation trends of international legal cooperation in criminal matters in an effort to create fast and smooth criminal proceedings in line with the highest standards of human rights protection, where much importance and significance is attributed to legal cooperation both within the European Union and in relationships with third countries.