The last decades have witnessed a growing emphasis on the relationship between environmental law and criminal law. Legislation aimed at tackling environmental crime has been adopted at national, EU, and international level and has been gradually evolving over time. These developments notwithstanding, the current legal framework faces a number of challenges in tackling the largely inter-related phenomena of transnational, organised and economic environmental crime. This study by Valsamis Mitsilegas and Fabio Giuffrida addresses these challenges by focusing on the role of the European Union- and more specifically its criminal justice agencies (Europol and Eurojust)- in tackling transnational environmental crime. The study analyses the role of Eurojust and Europol in supporting and coordinating the competent national authorities dealing with investigations and/or prosecutions on transnational environmental crime, and it shows that, for the time being, the full potential of these agencies is not adequately exploited with regard to fighting this phenomenon effectively