Knowledge of the diversity and distribution of tardigrades in Mexico is limited. Up to now 79 taxa of limno-terrestrial, freshwater and marine tardigrades were reported (including three species of Milnesium) from the country. We examined a total of 73 specimens of the genus Milnesium collected from mosses and lichens in northeastern Mexico. The analysed specimens represent four species, of which one was previously unknown, and is described in this paper. Milnesium fridaesp. nov. has eyes, claw configuration (CC) [3–3] - [3–3], a wide and short buccal tube (standard width on average 64% of its length), and cuticle with very small pseudopores visible under high magnifications. It differs from other Milnesium species by various morphometric characteristics specified in the paper. Moreover, the ontogenetic variability of CC in new species was followed, observing that there is no variability in this character. In addition, distribution of the Milnesium species in Mexico is also discussed.