The success of a weed’s biological pathway is dependent on several factors including the mechanism(s) of dispersal, longevity of seeds in the soil seed bank, adaptation to varying environmental conditions and, competitive and reproductive abilities. In Near East barley, some races can be identified as wild but in other races wild and weed forms are confounded. Wild barley has wider distribution than the wild wheat and is spread over a wide area in the East Mediterranean basin and West Asiatic countries. In the Fertile Crescent countries, Hordeum spontaneum occupies a whole array of secondary man-made habitats. Invasive weeds possess a variety of characteristics that enable them to disperse rapidly into new areas. A variety of both aboveground and belowground plant traits can be used for identifying invasive species. Wild barley has some considerable traits including high genetic variation, high allelopathic potential, high relative growth rate, root characteristics, high competitive abilities and, became an invasive species in many habitats of Iran. Further studies are essential to evaluate the other mechanism(s) of invasiveness of wild barley in alien environment. Key words: Wild barley, Hordeum spontaneum, habitat, distribution, invasive weed.