Abstract. The diversity of medicinal plants in Tended Nature Reserve “Atanasovsko ezero” has been studied. A total of 102 species and 1 subspecies belonging to 82 genera have been established. The data is indicative of the relatively great diversity of medicinal plants in Tended Nature Reserve “Atanasovsko ezero”. Most of the medicinal plants belong to Magnoliophyta. The families Asteraceae, Lamiaceae and Chenopodiaceae are represented by the greatest number of species and genera. A large number of antropophyte, melliferous and toxic plants has been registered. Five protected species and one subspecies were found: Anethum graveolens L.; Artemisia lerchiana Weber; Eryngium maritimum L.; Еuphorbia peplis L.; Orchis laxiflora ssp. еlegans (Heuffel) Soó; Samolus valerandii L. The populations of all registered medicinal plants are in good condition, especially those of perennial ruderal and weed plants. Certain reduction in the number of populations has been registered for Dictamnus albus L., Iris pumila L. and I. pseudacorus L. At this stage it is not necessary to implement additional measures for protection of medicinal species on the studied territory.