The district comprises five municipalities: Hjartdal, Midt-Telemark, Nome, Notodden, and Tinn.

[4][5] Historically, the district was made up of the three munincipalities/parishes of Hjartdal, Tinn, and Heddal, which were created in 1837 when the formannskapsdistrikt laws came into effect.

In 1860, Gransherad municipality was created from portions of Tinn and Hjartdal.

[6] More recently, the areas of Midt-Telemark and Nome have been included in Aust-Telemark as well, although they were historically included in the old Nedre Telemark district ("Lower Telemark"), but that district is not really used anymore in favor of the Grenland district name which has slightly different boundaries.

[5] Notable people from Aust-Telemark include Myllarguten (1801-1872), legendary fiddler from Sauherad, Klaus Egge (1906-1979), composer from Gransherad and Hans Herbjørnsrud (born 1938), author from Heddal.