The Graaff-Reinet Municipality was created by virtue of a proclamation dated 28 August 1845, published in Cape of Good Hope Government Gazette No 2071 of 29 August 1845. The first ordinary meeting of the Commissioners took place on 18 September 1845. In January 1969 the Municipality of Graaff-Reinet amalgamated with the nearby Municipality of Adendorp.

In 1994 Graaff-Reinet became part of the Eastern Cape Province. It forms part of the Dr Beyers Naudé Local Municipality, one of seven local municipalities that falls under the Sarah Baartman District Municipality (formerly Cacadu District Municipality).

The first form of administration in the area, which later constituted the Graaff-Reinet district, was an official appointed in October 1780 as "Commandant of the Lands in the East".

After numerous petitions to the Council of Policy a magistrate was eventually appointed for the Graaff-Reinet district on 13 December 1785.

The magistrate acted as chairman of the Slave Office, Clerk of the Peace, representative of the Orphan Chamber, chairman of the matrimonial court, etc.