Negative implications of indiscriminate use ofherbicides in agricultural systems have forced the scientific community to develop alternate weed control strategies. Allelopathy appears one of the possible alternatives for achieving sustainable weed management. Study was designed to evaluate the allelopathic potential of sunflower (Helianthus annuus L. cv. Azargol) water extracts on germination, early seedling growth and lipid peroxidation of Johnson grass (Sorghum halepnse) and wild mustard (Sinapis arvensis). Three levels of sunflower water extract viz. 5%, 10% and 15% were evaluated against both species in two separate experiments by using distilled water as control. Sunflower water extracts considerably delayed and reduced the germination percentage, along with fresh weight and length of both Johnson grass and wild mustard seedlings. Highest reduction was noticed at higher concentration (15%) of sunflower water extract. Nonetheless, sunflower water extract application enhanced malondialdehyde content (lipid peroxidation) along with reduced activities of antioxidants (catalases and peroxidases) in both Johnson grass and wild mustard seedlings. Such effects can be explored further under field conditions