On 1 January 1970, two uninhabited areas of Neset and Råbudal in the neighboring municipality of Froland were transferred to Birkenes (these areas were formerly in the municipality of Mykland prior to 1967). On 1 January 1979, the uninhabited area of Landheia in Froland was transferred to the control of Birkenes municipality. Later, on 1 January 1986, the Lislevand farm area (population: 8) was transferred from Birkenes to the neighboring municipality of Evje og Hornnes. Then on 1 January 1991, the Dalen area of Birkenes (population: 60) was transferred to the neighboring municipality of Froland. On 1 January 2019, the Hovlandsdalen area (population: 27) was transferred from Birkenes municipality to the neighboring Evje og Hornnes municipality.