The creation of the Duchy of Warsaw as a result of the Napoleonic wars in Europe created the need to reorganize the state administration to conform to modern models and meet the new challenges of a new era in European history. Alongside this, there was a need to reform the institution of the judiciary and remove from its practices outdated institutions imposed by the partitioners, namely Prussian models. This ambitious goal was set and carried out by Justice Minister Feliks Lubienski, to whom the Polish judiciary owes its introduction to the new era. Thanks to his work, it was possible to base the legal system of Poland at that time on the regulations of the Napoleonic Code. The present study outlines the institutions of the judiciary (courts and prosecutor's offices) that were created on the basis of modern legal and political solutions of the Napoleonic regulation, based on the tradition of Roman law, based on the foundations of Christian civilization and elements of Greek philosophy. This was an important impetus for the modernization of the judiciary in Poland and initiated the social and economic changes necessary for the smooth functioning of the modern Polish State