Grimmia jacutica is described as a new species. This species seems to be quite common in East Siberia and occurs also in some neighboring areas, ranging eastwards to Chukotka and Alaska. Many characters of G. jacutica are similar to Racomitrium species in the R. heterostichum group, and many specimens were found in herbaria under various names of Racomitrium. However the closest relative of G. jacutica is probably a Western North American endemic species G. leibergii Paris. The comparison between these two taxa and the detailed illustration of G. jacutica are given, and the distribution of G. jacutica is mapped.