peer reviewed ; The European Public Prosecutor's Office (hereafter EPPO) was established by way of enhanced cooperation, with the adoption of Council Regulation (EU) 2017/1939 (hereafter EPPO Regulation). It has the power to conduct criminal investigations and to directly act as the prosecuting authority before national criminal courts, which is revolutionary. Interestingly, the EPPO Regulation does not explicitly regulate the relation between the EPPO and national judges at the pre-trial stage, who may intervene punctually or, in some cases, even conduct the investigation. Indeed, some civil law systems have a system of shared investigative competences between the public prosecutor and the investigating judge, meaning that the latter conducts a judicial inquiry, while the former is responsible for the prosecution. This raises the delicate question whether a judicial inquiry is compatible with the EPPO Regulation. This article analyses this question, which hugely impacts the implementation of the EPPO, with respect to the Belgian legal system, based on a close reading of the EPPO Regulation and taking into account its drafting history. It will argue that the EPPO Regulation is not per se irreconcilable with a judicial inquiry as the Member States did not wish the EPPO Regulation to alter the way in which criminal investigations are organised at national level. Subsequently, it will examine how an EPPO investigation conducted by an investigating judge can practically function. While the analysis concentrates on Belgium, the underlying reasoning may also be useful for other Member States with a similar legal system.