Essential oils from air-dried leaves and verticillasters of Nepeta nuda ssp. nuda from Greece were analyzed by means of gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. The dominant constituent in the verticillaster oils was 4aα,7α,7aß-nepetalactone (75.7%). The main metabolites of the leaf oil were 1,8-cineole (16.7%), 4aα,7α,7aß-nepetalactone (24.7%), and caryophyllene oxide (16.3%). The oils were examined for their antioxidant activity. Neutralization of stable 2,2-diphenyl-1-picrylhydrazyl radical ranged from 10.83% (2.50 μg/mL) to 58.64% (50.00 μg/mL) for verticillaster oil and from 6.25% (2.50 μg/mL) to 57.79% (50.00 μg/mL) for leaf oil. The essential oil from verticillasters had significant effects on lipid peroxidation (in the range of 41.18-59.23%), compared to tert-butylated hydroxytoluene (37.04%). In contrast, the essential oil from leaves exhibited pro-oxidant activity at the highest concentration applied.