Seven Streptomyces spp. were screened for their potential to protect cucumber plants against Cucumber mosaic virus (CMV). Foliage treatment with the Streptomyces culture filtrates resulted in high reduction of the level of disease severity of CMV infection. In contrast, soil treatments were less effective in virus inhibition. Concerning foliage treatment, culture filtrates of S. griseorebens and S. cavourensis showed the highest inhibitory effect (90% and 85%, respectively) when applied 48 hrs prior to virus inoculation. On the other hand, soaking of cucumber seeds for 2hrs in the Streptomyces culture filtrates resulted in the highest viral inhibition. Generally, S. griseorebens recorded the highest percentage of viral inhibition (65%). Direct ELISA was carried-out as a diagnostic tool at the beginning and throughout this study. A number of de-novo synthesized proteins (induced proteins) were detected by polyacrylamide-gel electrophoretic analysis in cucumber leaves treated with culture filtrates of Streptomyces spp. relative to the control treatment. Considerable increase in total phenols as well as peroxidase and polyphenol oxidase activity levels in treated plants before virus inoculation were recorded comparing with the healthy and infected control plants. The highest values were observed in treated cucumber plants with S. griseorebens collected 14 days post virus inoculation.