Prosopis juliflora belongs to the family Fabaceae and is commonly known as mesquite. It has been used as a folk remedy for catarrh, cold, diarrhea, dysentery, excrescences, flu, hoarseness, inflammation, measles, sore throat, and in the healing of wounds. Its antibacterial, antioxidant, antifungal, antitumor, and anthelminitic activities are also reported and it contains phytochemicals such as flavonols, alkaloids, tannins, ellagic acid, glycosides, steroids, and various phenolic compounds. It is reported to be used as feed for cattle worldwide. The present study was conducted to investigate the in-vitro antioxidant (DPPH assay) and Preliminary phytochemical screening of ethanol extract of P. juliflora. The ethanolic leaves extract of P. juliflora was screened for antioxidant screening using 2.2Di (4-tert-octylPhenyl)-1-Picryl-Hydrazyl (DPPH), compared with p. galate as standard antioxidant. The tested antioxidant activity gave (61.55 ± 1.02 RSA %) in comparison to the control of propyl galate levels (88 ± 0.07RSA %) and the preliminary phytochemical screening of the leaves revealed that the plant contains Alkaloids, Flavonoids, Saponins, Tannins, Anthraquinone Glycoside and Coumarins.