The current chapter is dedicated to the assessment of the impact and expression of EU law in the development of substantive and procedural criminal law in Latvia over the last 20 years. The authors acknowledge that EU law has played an important role in the development of Latvian criminal law (both in substantive and procedural aspects), meanwhile there is no reason to unequivocally recognise that EU law has been the most frequent or decisive reason for amendments and changes in Latvian criminal legislation or the practice of its application. Describing the impact of EU law on the Latvian criminal justice system, the authors consider the main areas of its influence. In the area of substantive law, the focus is predominantly on criminalisation of offences as a consequence of EU requirements or recommendations, extension of the scope of certain criminal offences, as well as confiscation of instrumentalities and proceeds of crime. Two strands of influence are considered in relation to criminal procedural law: (1) cooperation (e.g., the European arrest warrant) and joint work (EPPO) in the EU criminal justice area; (2) the impact of EU law on the legal framework of so-called domestic or local criminal procedure.