Herein we report the phytochemical screening and gas chromatography–mass spectroscopy (GC-MS) of Amaranthus spinosus an annual plant that grows wildly in Nigeria, using standard methods. Dried powdered leaves of the plant were subjected to cold maceration in two polar solvents, water and ethanol. The phytochemical screening of the water extract reveals the presence of bioactive constituents viz. alkaloids, glycosides, flavonoids, tannins, saponins, terpenoids, steroids, anthraquinones, phenols, carbohydrates, proteins, and fats. While GC-MS analysis reveals peaks that represent ten different chemical compounds in the plant, two prominent compounds were identified: 1,5-methano-1H,7H,11H-furo[3,4-g]pyrano[3,2-b]xanthene-7,15-dione,3,3a,4,5-tetrahydro-8-hydroxy-3,3,11,11-tetramethyl-1, 13-bis(3-methyl-2-buten-1-yl)-,(1R,3aS,5S,14aS)- and 7,11-hexadecadienal as the most abundant constituents while the least abundant compounds were the 9-oxabicyclo[6.1.0] nonane and 7-octen-2-one.