The concert, which begins at 6:30 p.m., is set to be the group's biggest European performance and has been hailed as an "extraordinary event" by its organizers.
The Free Choir's repertoire features historical hymns of the Belarusian people, with a strong patriotic message.
This has set the ensemble on a collision course with the authorities in its native country, where patriotic songs are considered extremist, public broadcaster Polish Radio’s IAR news agency reported.
So far, 30 members of the choir have been jailed and persecuted, receiving convictions and heavy fines, according to the IAR news agency.
The group operates in strict secrecy and the singers perform in masks.
"These are artists from major Belarusian theatres," said Lesław Krzewski of Warsaw’s Royal Castle Museum, which is hosting the event.
"They sing Belarusian patriotic and folk songs that have provided the soundtrack to the protests” in that country against strongman President Alexander Lukashenko, he added.
Thursday's concert, organised by Warsaw’s Royal Castle with the Ogrody Muzyczne (Musical Gardens) Foundation, is dedicated to Belarusian dissident musician Maria Kolesnikova.
The flutist, conductor and opposition activist was arrested by the regime in Minsk last September, on charges of undermining national security and taking part in a conspiracy to seize power.
(pm/gs)
Source: IAR