After secondary school, Sigitas Tamkevičius started studying at the Catholic seminary in 1955. In 1957-1960 he served in the Soviet army, and in 1960 he continued his studies at the seminary. In 1962, Tamkevičius was ordained a Catholic priest. In 1962-1975, he served as a parish priest in the Lithuanian countryside. He became a Jesuit in 1968. In 1969, the Soviet government forbade him to serve as a priest, and he was forced to work in a factory. In 1972-1983, he initiated and edited the Chronicle of the Catholic Church in Lithuania. Tamkevičius established a committee for defending the rights of believers in 1978. In 1983 he was arrested and investigated by the KGB. In 1983-1988, he was imprisoned in a labour camp in Perm and Mordovia (Russia). During the national revival, Tamkevičius became head of the Catholic seminary, and in 1991 he was consecrated as a bishop by Pope John Paul II. In 1996 he became an archbishop, and in 2005-2014 he was chair of the Conference of Lithuanian Bishops. He served in this role until 2015.