Peanuts (Arachis hypogaea L.) represent one of the most vulnerable crops to infection by Aspergillus flavus under storage conditions. Accordingly, peanuts represent a major source of aflatoxin. The mycelial growth diameter of A. flavus was dramatically reduced by all tested plant extracts and their various concentrations as compared to the control. Thyme extract was the most effective in reducing the linear growth and the total aflatoxin production of A. flavus in vitro. Application of plant extracts on peanuts before the artificial infection with A. flavus under storage conditions showed high efficiency of reducing total aflatoxin production compared to the control. Thyme extract at concentration 5% was the most effective treatment in reducing total aflatoxin production. According to the protein electrophoresis results of A. flavus treated with rosemary, thyme, and basil plant extracts, thyme treatment caused the development of newly produced proteins with about 25 kDa molecular weights. Whereas in A. flavus isolate treated with rosemary, two bands with molecular weights of 63 and 75 kDa, respectively, entirely were vanished. Similarly, A. flavus isolate treated with basil resulted in disappearance of one band with molecular weight of 63 kDa.