We validate 1D glacial isostatic adjustment (GIA) models ICE-6G_C (VM5a) and ICE-7G_NA (VM7), and new 3D GIA models in the Russian Arctic against a quality-controlled deglacial relative sea-level (RSL) database. The 1D models correspond to the RSL data along the southern coast of Barents Sea and Franz-Josef-Land, but show notable misfits with the White Sea data. We find 3D models fit better than 1D models around the White Sea while retaining comparable fits in other regions of the Russian Arctic. Our results reveal (1) RSL in the western Russian Arctic is sensitive to laterally varying lithosphere and 3D viscosity structure in the upper mantle; and (2) RSL in the whole Russian Arctic is less sensitive to 3D viscosity structure in the lower mantle compared to the upper mantle. The 3D models reveal a compromise in the upper mantle between background viscosity and scaling factor to best fit the RSL data.