On 1 January 1867, an uninhabited part of Søndeled was transferred to the neighboring municipality of Dybvaag.

Later, on 1 January 1901, a small urban area of eastern Søndeled (population: 658) was transferred to the neighboring town of Risør.

[6] The municipality (originally the parish) is named after the local Søndeledfjorden (Old Norse: Sundaleið) since the first Søndeled Church was built there.

The first element is the plural genitive case of the word sund which means "sound" or "strait".

[8] The municipal council (Herredsstyre) of Søndeled was made up of 25 representatives that were elected to four year terms.