The effect of hydration of sodium-conducting solid electrolytes (SEs) on the reversibility of Na0.5WO3/Na+-solid electrolyte interfaces was studied. It was shown that solid electrolytes with higher tendency to hydration form the interfaces with higher room-temperature reversibility with respect to Na+ ions. According to IR spectra, the ability to hydration decreases in series Na5GdSi4O12>Na3Zr2Si2PO12>Na3SC2(PO4)(3). It is supposed that hydrated layers at the surfaces of solid electrolyte grains exhibit a more disordered structure than the bulk of the grains and, thus, promote the electrochemical reactions.