We explore marine reservoir effects (MREs) in seal bones from the northern Bering and Chukchi Seas regions. Ringed and bearded seals have served as dietary staples in human populations along the coasts of Arctic northeast Asia and North America for several millennia. Radiocarbon (14C) dates on seal bones and terrestrial materials (caribou, plants seeds, wood, and wood charcoal) were compared from archaeological sites in the Bering Strait region of northwestern Alaska to assess MREs in these sea mammals over time. We also compared these results to 14C dates on modern seal specimens collected in AD 1932 and 1946 from the Bering Sea region. Our paired archaeological samples were recovered from late Holocene archaeological features, including floors from dwellings and cache pits, that date between 1600 and 130 cal BP. 14C dates on seal bones from the northern Bering and Chukchi Seas show differences [R(t)] of 800 ± 140 years from to their terrestrial counterparts, and deviations of 404 ± 112 years (ΔR) from the marine calibration curve.