[1] The principal town and administrative centre lies at Saumlaki in Tanimbar Selatan District.

The regency was originally created from the western districts of Southeast Maluku Regency on 4 October 1999 as the "West Southeast Maluku Regency" (Kabupaten Maluku Tenggara Barat).

On 24 June 2008 the western districts of this Regency were split off to create the Southwest Maluku Regency (Kabupaten Maluku Barat Daya), leaving only the archipelago of the Tanimbar Islands in the West Southeast Maluku Regency, which was later renamed as Tanimbar Islands Regency (Kabupaten Kepulauan Tanimbar) on 23 January 2019 (2019-01-23); the legislation for this was passed on 28 January 2019.

Subsequently, a tenth district - Molu Maru (consisting of the two northernmost islands in the Tanimbars - Molu and Maru - with a combined land area of 63.8 km2) - was by 2017 created from part of the existing Wuorlabobar District.

[1] The table also includes the locations of the district administrative centres, the number of administrative villages in each district (totaling 80 rural desa and 2 urban kelurahan), and its postal code.