It is believed that its inhabitants are the same as the Brondings who are referred to in the Anglo-Saxon poems Beowulf and Widsith.

Brännö is mentioned in the Icelandic Sagas as the location of several important thing assemblies in the Viking Age and later.

People taken captive during the Viking raids in Western Europe, such as Ireland, could be sold to Moorish Spain via the Dublin slave trade[2] or transported to Hedeby or Brännö and from there via the Volga trade route to Russia, where slaves and furs were sold to Muslim merchants in exchange for Arab silver dirham and silk, which have been found in Birka, Wollin and Dublin;[3] initially this trade route between Europe and the Abbasid Caliphate passed via the Khazar Kaghanate,[4] but from the early 10th-century onward it went via Volga Bulgaria and from there by caravan to Khwarazm, to the Samanid slave market in Central Asia and finally via Iran to the Abbasid Caliphate.

[5] The Laxdæla saga relates that the beautiful Irish princess Melkorka was sold as a thrall to the Icelandic chieftain Hoskuld Dala-Kollsson, during a fair on Brännö, in the 10th century.

[6] The jetty on the island is also mentioned in the song De' ä' dans på Brännö brygga.