This study was conducted to evaluate the herbicidal activity of some plant extracts against three selected weeds (Amaranthus retroflexus, Cichorium intybus and Echinochloa crus-galli.) and also to be compared with the herbicide atrazine (gesaprim®, 80% WP). The plant extracts included: Allium cepa (Onion) lamina, Allium sativum (Garlic) lamina, Cichorium intybus (Chicory) (whole plant), Citrus aurantium (Sour orange) peel, Conyza aegyptiaca (Fleabane) (whole plant), Oryza sativa (Rice) straw, Triticum aestivum (Wheat) straw, and Zea mays (Corn) straw. Three sets of laboratory experiments were conducted. First, the plant species were water extracted and bioassayed using radish as a bioindicator plant. Then these plants were tested against the chosen weeds in six different concentrations (1%, 4%, 7%, 10%, 15%, and 20% w/v). Finally, weeds were subjected to the herbicide atrazine in four concentrations (3.75%, 1.875%, 0.9375%, and 0.46875% w/v). The results showed that the majority of screened plants inhibited germination of radish seeds in a percentage ca 40% or more. The concentration 25% of the recommended dose of atrazine (0.9375% w/v) was the most effective against germination of all target weeds. The herbicide atrazine was found to be more potent than all the tested plant extracts against all target weeds. As for the effect on Amaranthus retroflexus and Cichorium intybus, extracts of Citrus aurantium peel and Cichorium intybus, respectively were considered more promising since atrazine exceeded their potency with only 0.6 times. It was noticed also that the relative potency of atrazine and Oryza sativa extract (against Cichorium intybus) were nearly the same (1.1 time). Most the tested plant extracts were very weak as compared with atrazine against Echinochloa crus-galli.