The antioxidant capacity and-total phenolic content of Moringa stenopeiat leaf obtained from a private garden in Bahir Dar City and powdered Moringa leaf purchased from a supermarket in Bahir Dar City were ~udied. Preliminary qualitative screening for the major secondary metabolites of extracts of each sample obtained using chloroform, water! aqueous methanol (80%), and aqueous ethanol (80%) as extractants showed positive test with varying intensity for phenols, flavonoids, tannins, saponins, and alkaloids. It was observed that the aqueous methanol extract~containcd the maximum concentrations ofall'the phytochemicals screened. Use of Folin­ Ciocaltcu's phenol reagent (FCR) showed the total phenolic contents in terms of mg gallic acid equivalent per 100 g of dry weight or samples to be 92.82 ±LOI <Ind 75.52 J.. 2.28 for, respectively, powdered leaves of :H. stenopetal and powdered Moringa leaf purchased. The .. antioxidaru capacity or"thc samples were assessed by using ferric reducing antioxidant power •· Abstract (FRAT'}, radical scavenging by 2,2-diphcnyl-l-picrylhydrazinyl (DPPI-1) and conjugated diene hydropcroxide assays. For the antioxidant assays, the oxidation substrate (sunflower oil) with or without added antioxidant was kept for six and eighteen days at elevated (65°C) and room temperature, respectively. The well-known antioxidant vitamin E was also used for comparative purposes in the antioxidant assays. The antioxidant capacity or the powdered Moringa stenopetal leaf and purchased Moringa powder were found lo be, respectively, 442.0S:d 0.58 and 291.32± 15.52 mg of ascorbic. acid equivalent per 100 g of dry weight or antioxidant in the · F'RAP assay. The corresponding. values for the powdered Moringa stenopetal leaf and purchased Mortnga powder in the [)PPI I assay were found to be, respectively, 144.02±0.53, 138.75±1.05 g of ascorbic acid equivalent per l 00 g of dry weight of' antioxidant. The antioxidant activities of the samples were also determined using the peroxide value (PV}' and conjugated dicncs (CD} contents. The PV value at the end or storage period of 6 days at 65"C for the control (sunflower oil) was found lo be 28.5 'While the corresponding values for the substrate containing each of 2000 ppm of Moringo stenopetal and 1 l)IJIJ ppm of vitamin H were found to be 15.2, 17.3, respectively. On the other hand, aflcr storage for 18 days at room temperature, the PV for the