Intergeneric diversity of powdery mildews within the genus Phyllactinia in Azerbaijan was investigated using morphological approaches based on re-examination of herbarium specimens kept in Mycological Herbarium of the Institute of Botany (BAK), Azerbaijan National Academy of Sciences and collections of recent years. To contribute detail taxonomic analysis data given in literatures was revised. Modern taxonomic and nomenclature changes were considered. The host range and geographical distribution of species residing to the genus within the country were clarified. Consequently, 17 powdery mildew taxa were recorded, of which Ph. alnicola, Ph. ampelopsidis, Ph. babayanii, Ph. carpini, Ph. corni, Ph. fraxini, Ph. guttata, Ph. mali, Ph. marissalii, Ph. moricola, Ph. nivea, Ph. orbicularis, Ph. paliuri, Ph. phaseolina, Ph. populi, Ph. pyri-serotinae and Ph. roboris on 32 plant species from 11 families were listed. These families belong to the groups Asterids (Cornaceae, Oleaceae) and Rosids (Fabaceae, Betulaceae, Fagaceae, Salicaceae, Moraceae, Rhamnaceae, Rosaceae, Ulmaceae, Sapindaceae, Vitaceae), of which Rosids exceeds in number of host species. The family Rosaceae possess the large amount of host species, but specific affinity of genus Phyllactinia is considered to be to the family Betulaceae. In addition, Phyllactinia powdery mildews seemed to spread mainly in mountainous areas of Azerbaijan. The highest number of taxa was recorded in the districts belonging to the Southern-East Great Caucasus region of the country, followed by regions Middle Araz and Lesser Caucasus. The lowest number of Phyllactinia taxa was recorded from Kur lowland and Lankaran regions. During the present study, it was revealed that herbarium samples of 14 taxa of genus Phyllactinia are available in the BAK, information of which is provided in this article.