Antioxidant capacities of the essential oil extracted from parsley (Petroselinum crispum) were evaluated by three different in vitro assays: b-carotene bleaching assay, DPPH free radical scavenging assay and Fe2+-metal chelating assay. Results showed that the parsley oil (PO) possessed a certain degree of antioxidant activities in terms of b-carotene bleaching capacity and free radical scavenging activity, but its metal chelating capacity was negligible. The antioxidant EC50 values of the b-carotene bleaching assay and DPPH free radical scavenging assay of the crude PO dissolved in methanol were measured in about 5.12 and 80.21 mg/mL, respectively. However, these values were much weaker than those of BHT in 0.01 and 0.58 mg/mL, and of a-tocopherol in 0.01 and 0.10 mg/mL. Isolation and identification of the inherent antioxidants in PO involved using various chromatographic techniques including silica gel open column chromatography, normal phase-HPLC and GC–MS. Myristicin in PO was found as a dominant compound (32.75%) that exhibited a moderate antioxidant activity. Apiol was the second dominant compound (17.54%), but it might be the major contributor to the antioxidant activity of PO. These results suggest that the PO and its two major components can be potential alternative natural antioxidants.