At the present stage of development of the economies of different states, the problem of biological invasions is considered one of the top-priorities. A special place among the different areas of research of biological invasions is occupied by the study of the most aggressive and dangerous alien plants in Protected Areas, as they pose a threat to the conservation of ecosystems and their biodiversity. The paper provides information on the phytocenotic diversity of communities with Berberis aquifolium Purch in native - in North America, as well as data on the distribution and degree of naturalization of the species in Eurasia, Australia, and New Zealand. It is established that Mahonia in many regions has the status of an invasive species, it is found both in anthropogenic disturbed and in natural communities, inhabiting a wide range of ecotopes (forest parks, meadows, forests, coastal dunes, etc.). On the Southern Coast of the Crimea, communities with Berberis aquifolium Purch were identified in forest park stands, as well as in coniferous and mixed forests, which belong to the classes Erico-Pinetea, Quercetea pubescentis according to the Braun-Blanquet classification. Preliminary data on the invasion of the species in the natural communities of two Protected Areas (PAs) - "Yalta Mountain Forest" and "Cape Martyan" are presented. The species is most widespread at altitudes from 200 to 400 m above sea level in pine, oak-hornbeam-pine and oak-pine forests belonging to the class Erico-Pinetea . In the lower forest belt at an altitude of up to 200 m above sea level, it is found in the pubescent oak-hornbeam and ash-oak-dogwood communities with Juniperus excelsa , J. deltoides , and Pinus pallasianae , which are part of the class Quercetea pubescentis .