The present study aims to evaluate the antioxidant activity of Cakilemaritima, Centaureaglomerata, Juncusbufonius, Lactucaserriola and Reichardiatingitana collected from Egypt, as well as to characterize their allelopathic potential against Bidenspilosa L. Total phenolics, tannins, alkaloids, flavonoids and saponins were determined in the studied plants. The antioxidant activity was measured based on the reduction of DPPH. The allelopathic bioassays of germination and growth were assayed. L. serriola attained the highest values of phenolics, tannins and alkaloids compared. However, C. glomerata exhibited the highest values of flavonoids and saponins. The IC50values of the antioxidant inhibition for R. tingitana, J. bufonius, L. serriola, C. glomerata and C. maritima were 663.98 ppm, 1026.62 ppm, 1029.45 ppm, 3783.05 ppm and 4964.20 ppm, respectively. The aqueous extracts of L. serriola was completely inhibited the germination of B. pilosa at 20 mg ml−1. Moreover, the extracts of C. glomerata, R. tingitana, C. maritima and J. bufonius inhibited the germination of B. pilosa by about 79.80%, 64.65%, 49.49%and 39.39%, respectively.Similar inhibitory effects on radicle and plumule growth were observed. Although, L. serriola is commonly considered as a noxious weed, it may be used in controlling B. pilosa.