The Malangen fjord, a high Boreal/low Arctic fjord in northern Norway, reflects Atlantic Water heat flux. Studies of dinoflagellate cyst assemblages, reflecting the fjord surface water masses, have been performed on sediment cores and surface sediment samples in order to reconstruct the Late Holocene climate history. Four dinoflagellate cyst assemblage zones reflect the hydrological changes that took place in the Malangen fjord during the Late Holocene. The periods from c. AD 500 to 790 and c. AD 1500 to 1940, stand out as cold periods. The period from c. AD 790 to 1500 is characterized by warm saline water, whereas the period from AD 1940 to present is characterized by decreasing inflow of warm, saline water.