The municipality stretched from the village of Ytre Arna to Trengereid along the coast and then inland about 8 kilometres (5.0 mi) to the Espeland area.

On 1 January 1972, Arna was merged into the city of Bergen (along with the other neighboring municipalities of Fana, Laksevåg, and Åsane).

The name is the indefinite genitive case plural form of arinn which means "hearth" or "platform" or "cliff at the bottom of the sea".

[5] The municipal council (Kommunestyre) of Arna was made up of 37 representatives that were elected to four year terms.

The party breakdown of the final municipal council was as follows: The mayors (Nynorsk: ordførar) of Arna:[8]