Palaeoecological investigations of mires suggest that agriculture was established north of the Arctic Circle in Norway during the late Bronze Age (1100–500 b.c.) and Pre-Roman Iron Age (500–1 b.c.). The lack of archaeobotanical and archaeological investigations has made it difficult to assess the nature of this early agricultural expansion into the Arctic in any detail. Here we present the first well documented archaeobotanical investigation from north Norway that covers this agricultural pioneer phase. Remains of charred seeds show that barley (Hordeum) was already being cultivated in the late Bronze Age, and that wheat (Triticum) was introduced in the Pre-Roman Iron Age. Large amounts of crowberry (Empetrum) seeds are also typical of the Pre-Roman Iron Age and were obviously an important food plant at the time, at least locally. Charcoal rich layers dated to the late Bronze Age suggest that the local birch forest was initially cleared away with the help of fire, possibly related to a slash-and-burn cultivation practice. Lithostratigraphic and pollen-analytical results indicate that the cultivation practice of the Pre-Roman Iron Age was a form of bush-fallow system with intensive soil re-working alternated with long periods of fallow.