The old parish of Sirdal was first established as a municipality in 1849 when it was separated from the large municipality of Bakke.
 Initially, Sirdal had 1,804 residents.
On 1 January 1903, a small area of Sirdal (population: 63) was transferred to the neighboring municipality of Fjotland.
 On 1 January 1905, the municipality of Sirdal was dissolved and its territories were divided into two new municipalities: Tonstad (population: 828) and Øvre Sirdal (population: 753).
 These large, sparsely populated municipalities merged along with the Øksendal area of Bakke municipality to recreate the municipality of Sirdal on 1 January 1960.
 This time, Sirdal started out with a population of 1,426.
 On 1 January 1987, the Virak and Espetveit areas of northern Flekkefjord (population: 41) were transferred to Sirdal municipality.
The old parish of Sirdal was first established as a municipality in 1849 when it was separated from the large municipality of Bakke.  Initially, Sirdal had 1,804 residents. On 1 January 1903, a small area of Sirdal (population: 63) was transferred to the neighboring municipality of Fjotland.  On 1 January 1905, the municipality of Sirdal was dissolved and its territories were divided into two new municipalities: Tonstad (population: 828) and Øvre Sirdal (population: 753).  These large, sparsely populated municipalities merged along with the Øksendal area of Bakke municipality to recreate the municipality of Sirdal on 1 January 1960.  This time, Sirdal started out with a population of 1,426.  On 1 January 1987, the Virak and Espetveit areas of northern Flekkefjord (population: 41) were transferred to Sirdal municipality.
Sirdal