World War II interrupted the Philharmonic's activity and robbed the orchestra of much of its prominence in European musical life. The orchestra lost half its members to the war, as well as its elegant building, which had been erected and modeled after the Paris Opera at the turn of the century by Karol Kozłowski. Although the orchestra resumed its regular season in 1947-48, it had to wait until 1955 for its home to be finally rebuilt, albeit in a new style. When the building was dedicated on February 21, the Philharmonic was proclaimed the National Orchestra of Poland.
The conductor Witold Rowicki was responsible for helping modernize the ensemble and ensuring the orchestra cultivated Polish music both old and recent, as represented by the works of Chopin, Górecki, and Lutosławski, without failing also to refine its mastery of the world repertoire. At home, the orchestra performs in the Warsaw Autumn International Festival of Contemporary Music besides accompanying the final rounds of the Chopin International Piano Competitions, while abroad it has toured the five continents to critical acclaim.
The Philharmonic has recorded music for several anime series. Notable shows include Cowboy Bebop, Soukyuu no Fafner, Giant Robo: The Animation, Ah! My Goddess: The Movie, Princess Nine, Vision of Escaflowne, Wolf's Rain, Hellsing Ultimate, and most recently, Genesis of Aquarion. It has also recorded music for Namco's Ace Combat 5: The Unsung War, and together with the Hollywood Session Orchestra, for the SEGA action-RPG Phantasy Star Universe. It also recorded a big part of the Score for Avalon , and part of a performance is seen in the movie.