The essential-oil and fatty-acid composition of the aerial parts of Ficaria kochii (Ledeb.) Iranshahr & Rech.f. native to Iran, and the antioxidant activity of various extracts of this plant were examined. The study by GC-FID and GC/MS analysis of the essential oil resulted in the identification of 61 compounds, representing 86.01% of the total oil composition. Phytol (10.49%), farnesol (7.72%), methyl linoleate (5.57%), and α-farnesene (4.96%) were the main components. The fatty-acid composition of the aerial parts of F. kochii was also analyzed by GC/MS. The major components were palmitic acid (25.9%), linolenic acid (25.3%), and linoleic acid (17.5%). Polyunsaturated fatty acids (PUFAs) were found in higher amounts than saturated fatty acids. The possible antioxidant activity of various extracts (prepared by using solvents with different polarity) of the F. kochii aerial parts was evaluated by screening for their 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity, FeIII-reducing power, total antioxidant activity, and inhibitory activity in the linoleic acid-peroxidation system. H2O proved to be the most efficient solvent for the extraction of antioxidants, as the H2O extract contained the highest amount of phenolic compounds (2.78±0.23 GAE/g dry matter) and also exhibited the strongest antioxidant capacity in all the assays used. The results of the present investigation demonstrated that the aerial parts of F. kochii can be used as natural and safe nutrition supplement in place of synthetic ones.