The Susedgrad park forrest site belongs to the legally protected area of the Medvednica Nature Park, and includes the ruins of the old town of Susedgrad. The vascular flora was investigated for the first time during the vegetation seasons of 2020 and 2021. A total of 164 taxa (species and subspecies) of vascular flora were recorded. The species are herbariumed, digitized and available online on the ZAGR Herbarium (http://herbarium.agr.hr/hr). The inventoried flora belongs to 56 families, of which the most represented are: Asteraceae and Lamiaceae each with nine taxa (6 %), Apiaceae, Brassicaceae, Cichoriaceae and Ranunculaceae each with eight taxa (5 %). The largest relative representation among life forms are hemicryptophytes (H) with 46 %, followed by phanerophytes (P) with 16 % and therophytes (T) with 15 %. Mostly dominant of the arctic and sub-atlantic floral element (27 taxa; 16,5 %) and of the sub-atlantic and eurasian (16,5 %). It is noticeable that in the area of Medvednica several phytogeographical areas overlap from the phytogeographical aspect. The inventory recorded five invasive and eight endangered plant taxa. The results of this research can serve as a basis for potential further research related to biodiversity, evaluation and preservation of the environment and the possibility of sustainability of urban, natural ecosystems.