The results of phytopathological observations of trees and shrubs in the parks of the State Museum-Reserve Peterhof are presented. Collection of material and analysis of the plant diseases distribution were made in the summer-autumn periods of 2013- 2017 (Upper Garden and Lower Park in Peterhof, Lower Garden and Upper Park of Oranienbaum). The Alexandria Park and the Kolonistsky Park were included in the research in the summer of 2018. A 120 species of fungi (micro- and macromycetes) were found on trees and shrubs in the parks. The majority of the species (97) were micromycetes. Some of them were associated with diseases such as powdery mildew, spotting, rust, and necrosis. Saprotrophic species were also observed. Most often micromycetes were found on dry branches and live leaves. Powdery mildew was found on the leaves of oak, maple, alder, pea shrub, hawthorn, lilac, viburnum, and elder. In most cases, the disease had moderate development, but covered large areas. Leaf spots occur locally. In some cases, they had a focal character. Some diseases of linden, larch, and elm were characterized by high severity. Sporulation of the causative agent of thyrostromosis was registered everywhere on the branches of linden in the alleys plantings as well as on single standing trees. In total, 23 species of xylotrophic macromycetes were identified. In regular parts of parks xylotrophs were found more commonly on living trees. Species from order the Polyporales were predominant. A distribution map of macromycetes in the Lower Park is presented. Possible factors affecting the distribution and development of fungal diseases of trees and shrubs on the territory of State Museum-Reserve Peterhof are discussed. The distribution of pathogenic fungi in the biocenoses of parks can be characterized as irregular. It could be attributed to the composition and density of plantations, the degree of anthropogenic influence on some areas, and features of the current plant care.