Abstract: Viscum album is a hemiparasitic shrub on a wide range of wood species. The bacterialand fungal communities of Viscum album subsp. album and three different host species (Malusdomestica, Juglans nigra and Acer tataricum) were analysed by cultivation dependent methods.Endophytes were isolated from leaves and seeds of Viscum album as well as from branches of thehost trees on five different growing media. The isolated endophytes were screened forantagonistic effects i) against plant pathogens (Alternaria alternata, Botrytis cinerea,Phytophthora infestans, and Sclerotinia sclerotiorum), and ii) against clean room inhabitants orpathogens (gram- positive bacteria: Staphylococcus epidermidis, Propionobacterium acnes,Paenibacillus polymyxa, Geobacillus stearothermophilus, Bacillus pumilus; gram-negativebacteria: Stenotrophomonas maltophilia, Escherichia coli, Pseudomonas aeruginosa; fungi:Verticillium dahliae, Aspergillus niger, Candida albicans) by dual culture assay. Beside the highproportion of antagonistic isolates against both groups in general, we found similarities but alsoclear differences between parasite and host. Mistletoes, especially the seeds, contained a higherantagonistic potential than the host plants. Plant-associated endophytic microorganisms fromparasitic plants are an interesting bio-resource to control plant pathogens but also clean roominhabitants/pathogens.