Abstract: Wet rot-diseased Citrus sinensis fruits were collected from Kafr El-Ziat Station for citrus exportation. The fungal pathogen was isolated and identified as Penicillium italicum. Sixty eight bacterial isolates (eubacteria and actinomycetes) were screened for their antagonistic activities against the fungal pathogen, Penicillium italicum. Thirty one isolates (identified and unidentified) showed antifungal activity against the pathogen and unidentified actinomycete isolated from the rhizosphere of Citrus sinensis trees, exhibited the highest activity. Cultural, physiological and biochemical studies were performed to characterize and identify the most active actinomycete. Depending on the results of these studies, the most active antifungal actinomycete was identified as Streptomyces alni. The sterilized cultural filtrate of Streptomyces alni was applied to Citrus sinensis fruits and inhibited the fungal infection until 27 days of storage, but slight symptoms of infection appeared after one month of storage under humid conditions.