 Giedraitis was ordained as a priest in 1571.In February 1572, Protasewicz raised Giedraitis to members of the cathedral chapter and put him in charge of church property ("custos").When Bishop of Samogitia Jurgis Petkūnas died in July 1574, Jakub Uchański, Primate of Poland and Archbishop of Gniezno, attempted to promote his nephew Jakub Woroniecki to the vacancy.