In 1931, several osseous and lithic artefacts, as well as fish and whalebones, were discovered in the wetland at the Jortveit farm in Southern Norway. In 2018–19, a small-scale excavation at the original find location took place and a series of AMS-dates were produced. The excavation identified a mud profile with exceptional preservation conditions. At ∼125–130 cm depth, the mud contained unburnt fish and whale bones, burnt wooden sticks and lithic artefacts. AMS-dates of stray finds and samples retrieved during the excavation date to the period roughly between 3700–2500 cal BCE, i.e. Scandinavian Early and Middle Neolithic Periods. Nearly all bones belong to the Atlantic bluefin tuna (Thunnus thynnus). The results are compared to local climate and landscape reconstructions, and the question of marine adaptation in the Neolithic is discussed. We find that the Jortveit site represented a patch in the landscape for specialized marine adaptation in the Neolithic.