The present study gives an overview of the flora of Hustai National Park, which hosts southern outposts of boreal forests embedded in a matrix of typical steppes. We address floristic composition, life forms, ecological groups and geographical elements, and compare our data against studies from broadly similar regions. A total of 493 vascular plant species belonging to 246 genera and 65 families were recorded. The biggest plant families are Asteraceae (67 species) followed by Poaceae (56 species), Fabaceae (51 species), and Rosaceae (33 species), while 21 families were represented by only one species each. Mesophytes (32.5%) and xerophytes (25.4%) were the most frequent ecological groups, indicating a typical mountain steppe environment. Most species were hemicryptophytes (56.8%), followed by therophytes (18.7%) and cryptophytes (geophytes 10.5%), while the least frequent life form classes were chamaephytes (5.1%) and helophytes (0.2%). Asian chorological elements constituted 52.3% of the total flora, while Eurasian account for 30%, Holarctic for 14.8%, Asian-American for 1.4% and Cosmopolitan for 1.4%. The Hustai mountain range thus represents a key example of the transition zone between the relatively moist Taiga forests and the drier steppe grasslands. These climate transitional zones are very sensitive to changing climate and land use.