In a land area of 11,050 square kilometers, the diocesan territory covers four districts namely East Sumba, Central Sumba, West Sumba, and Southwest Sumba.
Catholics in the diocese consists mostly of Flores people and a few of Javanese.
Catholicism in Sumba was firstly introduced by Jesuit missioners on April 21, 1889. Two Jesuit priests and a Jesuit brother had since worked in Sumba.
But in 1898 the mission in Sumba was closed and the Jesuit missioners went to Java.
Divine Word missionaries then came to Sumba in 1929. Thirteen priests and a brother had worked there during 1929-1957.
On May 16, 1957, mission of Sumba was taken by Redemptorist missioners. Divine Word priests went back to Flores. Congregations of religious men and women have since come and worked in Sumba.
On Oct. 20, 1959, the apostolic prefecture of Weetembula was established and elevated into diocese on Feb. 6, 1969. Divine Word Father Gerulfus Kherubim Pareira was appointed as its first bishop and ordained on April 25, 1986. The prelate then was appointed as the bishop of Maumere on Jan. 19, 2008. Redemptorist Father Edmund Woga was appointed to succeed him on April 4, 2009 and ordained bishop July 17, 2009.