The article presents the relationship between civil law reforms and administrative reforms in the Duchy of Warsaw. In both these areas, the reforms carried out in the Duchy of Warsaw consisted in the transfer of solutions based on French models to the Duchy of Warsaw, almost completely disregarding the existing Polish solutions. The introduction the Napoleon’s Code, the French Code of Civil Procedure and the French Commercial Code to the Duchy had an impact not only on the applicable law, but also on the organization of the judiciary as well as administration and administrative division in the Duchy. The most important role was the introduction of the Napoleonic Code, which despite many objections, thanks to Minister of Justice Feliks Łubieński, became the law in force in the Duchy, and survived even its collapse, exerting a significant influence on the further development of civil law in Poland. On the other hand, administrative reforms did not have such opportunities, although administrative reforms became the nucleus of modern administration in Polish territories.