The present investigation was conducted to study the allelopathic effects of some Sinai's Flora (Seriphidium herba-alba Asso and Achillea fragrantissima Forssk) aqueous extracts on seed germination and weed control growing in olive orchards. Plant aqueous extracts at 5, 15 and 25% concentrations and tap water as a control were applied alone or in combination with  commercial herbicide named SUN UP^® 48% SL (the effective compound was Glyphosate ammonium) were used at 2.5 L. feddan^-1 (1:1) under field and laboratory conditions. Data indicated that the total fresh and dry weight of weeds was decreased significantly by increasing the concentration level of the extracts. The herbicide was the superior treatment in eradicating annual, biennial and perennial weeds, followed by A. inculata 25%+ Sun Up which achieved reasonable suppression for most annual, biennial and perennial weeds compared to the control. The extracts of S. herba-alba 25% + Sun Up inhibited the germination of most weeds (biennial and perennial).