A coarse clastic barrier and backing lagoon at Bay of Carness, Orkney, Scotland, United Kingdom, are examined. Mapping and survey of the landforms and sediments associated with the barrier and lagoon, followed by stratigraphical investigation and laboratory analyses including pollen analysis, plant macrofossil analysis, diatom analysis and radiocarbon dating are described. The earliest dated event recorded is the development of a saltmarsh across fluvial sands as relative sea level was rising at 6560±50 radiocarbon years before present (BP). At this time, the barrier had begun to develop. By 5470±210 BP, the saltmarsh was replaced by largely freshwater lagoonal silts, reflecting the isolation of the head of the bay when the barrier formed across the bay as a swash aligned feature. As the lagoonal sediments continued to accumulate, barrier rollover was probably occurring, and both lagoonal and underlying saltmarsh sediments were either obscured or eroded at their seaward margins. At a time unknown, barrier movement landward ceased and the barrier stabilised, although there is some evidence that it might become unstable in the future. Pollen and plant macrofossil analysis from the saltmarsh and lagoonal sediments record the changing vegetation dynamics and pollen analysis reflects the impact of Neolithic activity after 4860±120 BP. The available evidence for relative sea level change at Bay of Carness is compared with evidence from Wick, to the south, and with a recent model of glacio-isostatic uplift which includes the area.