Gymnostomiella occupies an isolated position within the Pottiaceae. Zander (1993) considered it “.. without obvious close relatives, ..” and positioned it in the subfamily Merceyoideae tribe Barbulae between Scopelophila and Didymodon. He also noted a possible relationship of the genus to the subfamily Pottioideae through Chenia and Hennediella. Unusual features of the genus in Central America include its moniliform axillary hairs and ellipsoid gemmae often clustered in terminal cups. The absence of costal stereid cells, a stem central strand, and perichaetial/perigonial paraphyses are also distinctive features of the genus. Zander (1993) attributed central, substereid cells to the costa, a large central strand in the stem, variably present stomata, and moniliform perichaetial paraphyses to the genus world-wide.

Gymnostomiella and Splachnobryum have often been associated (Fleischer 1923, Brotherus 1924, Bartram 1939, Crum & Bartram 1958, Breen 1963, Gangulee 1974, Crum & Anderson 1981) because they have similar leaf shapes, costal forms, leaf areolation, and lack perichaetial/perigonial paraphyses. Splachnobryum differs from Gymnostomiella in having smooth leaf cells, clavate axillary hairs, anacrogynous development, naked archegonia, conic opercula, and a haplolepideous peristome (Allen & Pursell 2000).

Gymnostomiella was revised in the Neotropics and eastern Asia by Redfearn (1991). Arts (1998) provided a world-wide revision of the genus.