He was appointed Bishop of Iringa on 21 November 1992 by Pope John Paul II.
[1][2] He was appointed Coadjutor Bishop of the Roman Catholic Diocese of Sumbawanga, Tanzania on 14 November 1988.
On 6 January 1989, he received episcopal consecration at the St Peter's Basilica in Rome.
From 15 May 2013 until 18 May 2014, Bishop Tarcisius Ngalalekumtwa served as the Apostolic Administrator of the Roman Catholic Archdiocese of Songea.
[3] In 2017 Bishop Tarcisius Ngalalekumtwa was the president of the Tanzania Episcopal Conference (TEC).