The relationship between parental care patterns and mating system in voles has not been fully elucidated. Whereas mating and parental strategies has been reported for many New World vole species, such information is lacking for most Palearctic voles. Nothing is known about the social organization of Microtus mongolicus inhabiting mesic habitats of Central Asia. We investigated spacing of free-ranging M. mongolicus in Zabaikalsky Kray using mark-recapture method, and we assessed the parental care exhibited by Mongolian voles in laboratory. Home ranges (HR) and movement distances of overwintered males exceeded those of other categories of voles. HR overlapped within sexes and between sexes in linear habitat at high population density as well as in non-linear habitat at low-density. The revealed pattern of spacing is consistent with promiscuous mating system. In laboratory, both the parent-litter separation tests and undisturbed observations of animals in large enclosures showed that most males displayed paterna