The antioxidant activities of the ethanol, petroleum ether, ethyl acetate, n-butanol and water extract fractions from the seeds of papaya were evaluated in this study. The ethyl acetate fraction showed the strongest DPPH and hydroxyl free radical-scavenging activities, and its activities were stronger than those of ascorbic acid and sodium benzoate, respectively. The n-butanol fraction demonstrated the greatest ABTS⁺ radicals scavenging activity. The ethyl acetate fraction and the n-butanol fraction not only showed higher antioxidant activities than the petroleum ether fraction, water fraction and ethanol fraction, but also showed higher superoxide anion and hydrogen peroxide radicals scavenging activities than those of the other extract fractions. The high amount of total phenolics and total flavonoids in the ethyl acetate and n-butanol fractions contributed to their antioxidant activities. The ethyl acetate fraction was subjected to column chromatography, to yield two phenolic compounds, p-hydroxybenzoic acid and vanillic acid, which possessed significant antioxidant activities. Therefore, the seeds of papaya and these compounds might be used as natural antioxidants.