The chemical composition of the hydro-distilled essential oils of leaf, flower, stem and root of Ageratum conyzoides L. were analyzed by gas chromatography equipped with flame ionization detector (GC-FID) and gas chromatography coupled with mass spectrometry (GC-MS). A total of 42 constituents have been identified accounting 99.0 % (leaf), 97.3 % (stem), 98.3 % (flower) and 96.6 % (root) of the volatile compounds. The major constituents were 6-demethoxy-ageratochromene (precocene I) and Î²-caryophyllene dominated in leaf (72.3 %; 12.1 %), stem (66.5 %; 10.2 %), flower (50.3 %; 14.6 %) and root (79.3 %; 6.0 %) essential oils. The compound ageratochromene (precocene II) was found relatively high amount in flower (10.5 %) than leaf (3.1 %), root (0.4 %) and stem (0.3 %) oils. The occurrence of androencecalinol is being reported for the first time in leaf, flower, stem and root oils in low quantity (0.7 - 0.3 %).