He was ordained a Catholic priest and later rose through the ranks as Bishop of Vilnius eventually becoming a cardinal.

He was a close friend and adviser of King Sigismund III and represented his interests in front of the Pope.

He was elevated to the cardinalate by Pope Gregory XIII only on 12 December 1583 and was assigned the titulus of S. Sisto on 14 July 1586.

He participated in the 1587 election of King Sigismund III Vasa and became his trusted adviser.

: F. Machay pastoral activity Cardinal Radziwill, Bishop of Cracow (1591–1600), Kraków 1936 extra, O. Halecki "From florence to Brest (1439–1596)," The Sacred Poloniae Millennium, t 5 (1958).