Composition of biologically active substances in methanol extracts from the flowers and leaves of Achillea asiatica Serg. plants was examined in representatives of native flora from Siberia and Kazakhstan growing in different regions of Russia (Kemerovo and Khakasiya) and Kazakhstan. Gas chromatography integrated with mass spectrometry and used for analysis of the extracts from flowers and leaves showed considerable differences in the composition and content of mono-, sesqui-, and oxygen-containing terpenoid compounds associated with the region of occurrence. In the examined samples, antioxidant activity in the extracts from flowers of A. asiatica was much greater than in the extracts from leaves. Antioxidant efficiency of the extracts predominantly depends on phenol compounds that do not belong to terpenes. Phytochemical analysis of three samples of A. asiatica taken from different natural habitats showed a pronounced variation in the composition of biologically active substances and their antioxidant activity. This may account for a different medicinal effect of collected A. asiatica grass.