After the re-establishment of Poland's independence following World War I, it was (with a hiatus, 1922–26) the residence of Marshal Józef Piłsudski, Chief of State (1918–22) and later (1926–35) Minister of Military Affairs of Poland, who died there in 1935. (During the May 1926 coup d'état, President Stanisław Wojciechowski had abandoned it ahead of Piłsudski's advancing forces.)
During World War II, the building was extensively remodeled for Ludwig Fischer, Governor of occupied Warsaw in the "General Government" of Poland. It remains one of the few original structures in Warsaw to survive World War II.
In 1945-1952 it was the residence of Bolesław Bierut, and later of the president of the Council of State. From 1989 to July 1994, it was the official residence of Poland's president, but proved too small for that purpose.
Protection of the Belweder Palace by the Government Protection Bureau (Biuro Ochrony Rządu, abbreviated BOR) was difficult, as the palace is located on a hill that shares a fence with the popular Łazienki Park, located below, a major tourist attraction. For security reasons, the park has had to be partly closed during visits by foreign heads of state to the Belweder. Due to the size of Łazienki Park, this has proven difficult and time-consuming, and the Polish press has mocked Secret Service agents checking the bushes and disturbing the Park's peacocks.
Belweder is normally used by the President and the government for ceremonial purposes, while the President resides at the "Presidential Palace" in the city center. It also serves as an official residence for heads of state on official visits to Poland and other important guests. There have been plans to turn the Belweder Palace into a museum dedicated to Józef Piłsudski. Currently it houses a small exhibition devoted to the Marshal. However, the current president of Poland, Bronisław Komorowski, has chosen to make Belweder his official residence.