
Subdivisions of the Duchy of Warsaw were based on departments that were headed by prefects. The subsidivions were based on the French model following the erection of the Duchy of Warsaw by Napoleon. The departments were in turn subdivided into traditional Polish powiats (counties). Initially six departments were created out of the province of South Prussia in the Kingdom of Prussia. After the 1809 Polish–Austrian War, and the Treaty of Schönbrunn, their number increased to ten. Each department was named after its capital city.

Bydgoszcz Department was a unit of administrative division and local government in Polish Duchy of Warsaw in years 1806–1815.

Kalisz Department was a unit of administrative division and local government in Polish Duchy of Warsaw in years 1807–1815.

Kraków Department was a unit of administrative division and local government in Polish Duchy of Warsaw in years 1809–1815.

Łomża Department was an administrative division and local government in the Polish Duchy of Warsaw in the years 1807–15. The Department comprised 10 counties and had its capital at Łomża.

The Lublin Department was a unit of administrative division and local government in Polish Duchy of Warsaw in years 1810-1815. Its capital was Lublin. The division contained 10 counties. In 1815 it was transformed into the Lublin Voivodeship.

Płock Department was a unit of administrative division and local government in the Polish Duchy of Warsaw from 1806 to 1815.

Poznań Department was a unit of administrative division and local government in Polish Duchy of Warsaw in years 1806-1815.

Radom Department was a unit of administrative division and local government in Polish Duchy of Warsaw in years 1809–1815.

Siedlce Department was a unit of administrative division and local government in Polish Duchy of Warsaw in years 1809–1815.

Warsaw Department was a unit of administrative division and local government in Polish Duchy of Warsaw in years 1806–1815.