The venom of Chrysaora quinquecirrha (sea nettle) contains several toxins that have bioactivity in mammals. In our study we aimed to extract proteins from Chrysaora quinquecirrha and to test the antioxidant potential of both crude protein and purified fractions. Proteins extracted from sea nettle nematocyst venom were purified through Sephadex G-100 column chromatography. The molecular weight of purified proteins was determined by gel filtration and SDS-PAGE and was found to be 105, 65, and 9 kDa for Frc-1, Frc-2, Frc-3, respectively. The in vitro antioxidant potential of Chrysaora quinquecirrha was evaluated in different systems viz. radical scavenging activity by DPPH reduction, superoxide radical scavenging activity in PMS/NADH-NBT system, hydroxyl radical by Fe(3+)-Ascorbate-EDTA-H2O2 system and nitric oxide (NO) radical scavenging activity in sodium nitroprusside/Greiss reagent system. Frc-3 displayed the maximal antioxidant activity and found to have different levels of antioxidant properties in the models tested. In scavenging hydroxyl radicals, its activity was intense (IC(50) = 50.8 μg/mL) while in scavenging NO radical, it was moderate (IC(50) = 381.4 μg/mL).