Animals of most species avoid close inbreeding, but the level of incest avoidance varies, and the ultimate causes of interspecies differences in the inbreeding tolerance are not quite clear. The subterranean lifestyle is associated with several characteristics which, in theory, should weaken incest avoidance. The available empirical data do not allow testing this prediction. In this laboratory study, the inbreeding avoidance in a strictly subterranean species, Zaisan mole vole (Ellobius tancrei) was estimated. The results provided evidence for incest avoidance between virgin female and closely related male (brother or father), whereas mother–son pairs displayed inbreeding tolerance. The odds ratio for the reproduction in unrelated vs sibling pairs was further used as a proxy index of inbreeding avoidance level to compare this characteristic in E. tancrei and 11 non-subterranean voles. In agreement with the predictions, (i) among non-subterranean voles, monogamous species displayed stronger incest avoidance than polygamous species; and (ii) subterranean monogamous species, E. tancrei, displayed higher inbreeding tolerance than non-subterranean monogamous species.