Five commercial composts were evaluated to suppress the root-rot pathogens (Fusarium solani(Mart.) App. and Wr,Pythium ultimumTrow,Rhizoctonia solaniKuhn, andSclerotium rolfsiiSacc.) of cucumber plants underin vitroand greenhouse conditions.In vitrotests showed that all tested unautoclaved and unfiltrated composts water extracts (CWEs) had inhibitor effect against pathogenic fungi, compared to autoclaved and filtrated ones. Also, the inhibitor effects of 40 bacteria and 15 fungi isolated from composts were tested against the mycelial growth of cucumber root-rot pathogens. Twenty two bacteria and twelve fungal isolates had antagonistic effect against root-rot pathogens. The antagonistic fungal isolates were identified as 6 isolates belong to the genusAspergillusspp., 5 isolates belong to the genusPenicilliumspp. and one isolate belong to the genusChaetomiumspp. Under greenhouse conditions, the obtained results in pot experiment using artificial infested soil with cucumber root-rot pathogens showed that the compost amended soil reduced the percentage of disease incidence, pathogenic fungi population, and improved the cucumber vegetative parameters as shoot length, root length, fresh weight, and dry weight. These results suggested that composts are consequently considered as control measure against cucumber root-rot pathogens.