Azadirachta indica (neem) belonging to Meliaceae family is very important medicinal plant which is traditionally used to treat different diseases. The objective of this study was to evaluate in vitro antioxidant activity and characterize the chemical constituents in different crude extracts of the leaves of Azadirachta indica (neem) by using modern sensitive gas chromatography–mass spectrometry (GC–MS). The evaluation of antioxidant activity of different crude extracts was determined by DPPH (2,2-diphenyl-1-picrylhydrazyl) method. GC–MS analyses showed that majority of these identified compounds in various crude extracts contain normal hydrocarbons, phenolic compounds, terpeniods, alkaloids and glycosides. The high percentage of compounds that were identified in the crude extracts are chemically and biologically important. The evaluation of antioxidant capacity of different crude extracts was in the order of chloroform > butanol > ethyl acetate extract > hexane extract > methanol extract. The important chemical constituents were present in the leaf crude extracts of neem that can be endorsed to cultivation on a domestic plantation. The appropriate crude extracts for selective bioactive organic compounds can be chosen on the basis of GC–MS analysis. Therefore the identified good number of chemical compounds from various extracts of neem might have some ecological benefit for different aliments. Result from this study suggested that the chloroform crude extracts of neem could be used as a natural antioxidant.