Changes of the relative sea level (RSL) are among the drivers of coastal dynamics in the Arctic, along with hydrometeorological conditions, including air and water temperature, wave energy, storm frequency, ice-free period duration and other parameters, and morphological, geological and permafrost properties of the coasts. In the western Russian Arctic, patterns of modern and past RSL changes are highly variable, mainly depending on the interplay between the eustatic sea level changes and glacioisostatic adjustment (GIA). While coasts of the Kola Peninsula, Karelia and Franz-Josef Land and Novaya Zemlya archipelagoes were covered by an ice sheet during the Last Glacial Maximum (LGM), and experience post-glacial RSL fall, coasts of the Kara sea and Laptev seas were not covered by land-based ice masses and show sea level rise. Here, we analyze how the changing RSL influences coastal morphology and dynamics, based on literature data on past and present RSL changes in previously ice-covered regions and those regions which were ice-free at the LGM. We also observe results of satellite imagery processing allowing to calculate modern average coastal erosion rates in the Arctic in different conditions in terms of RSL and GIA. We show that the difference in coastal morphology and dynamics depends on the trend (RSL fall or rise). If areas with the same trend, but different rates are compared, RSL becomes a secondary driver, and the difference in erosion rates mainly depends on the interplay between the modern hydrometeorological conditions and permafrost properties of the coasts.