Auxiliary Bishop-designate Marek Solarczyk, 44, will assist Bishop Henryk Hoser.
He had been serving as pastor of the cathedral.
The Diocese of Warszawa-Praga has more than 1 million Catholics, served by some 640 priests and 1,500 religious.
Marek Solarczyk was born in Wolomin, Poland, in 1966 and ordained a priest in 1992.
