Background: Safety and efficacy of the synthetic antioxidants used in the food industry are frequently questioned because such antioxidants are unstable and highly volatile, therefore, interest in finding naturally occurring antioxidants that have the potential to protect human beings from damage induced by oxidative stress has intensified. Objective: Bioactivities of Thymus daenensis and Anethum graveolens essential oils with special reference to their antioxidative properties are studied. Methods: Total phenolic content (TPC), lipid peroxidation inhibition (LPI), ferrous-ion chelating (FIC), superoxide anion and nitric oxide radical scavenging, and tyrosinase inhibition activities of the essential oils were determined. Results: TPC of T. daenensis and A. graveolens oils were 644.07±6.79 and 174.91±2.05 mg GAE/100 g. T. daenensis and A. graveolens oils showed the highest LPI activity with FICs of 63.28±0.21 and 70.22±1.9 percent respectively. Superoxide anion and nitric oxide radical scavenging activities of the above oils had IC50 of 0.013, 0.001 and 0.005, 0.0014 mg, respectively. A. graveolens oil showed 6 fold higher anti - tyrosinase activity than T. daenensis oil. Conclusion: There was not correlation between lipid peroxidation or ferrous ion chelating activities with total phenolics implying that the oils contain chelating ligands. The effects of antioxidant phytochemicals in the biological systems are ascribed on their ability to scavenge radicals, chelating metals, activate the antioxidant enzymes, and to inhibit the oxidases. T. daenensis and A. graveolens oils have good commercial potential in both food processing and cosmetic industries.