The Nilgiri hills consist of a well-defined plateau situated at the junction of the two great ranges of hills, Eastern and Western Ghats. Asteraceae is one of the largest families having medicinal and aromatic plants in Nilgiris. The milk thistle plant, Silybum marianum is an annual or biennial plant, native to the Mediterranean area and some parts of the United States; this has now spread to other warm and dry regions. To investigate the phytochemicals, FT-IR and GC-MS analysis of ethanol extracts of Silybum marianum was done. Seeds were shade dried and finely powdered for ethanolic extraction. Then, each of the extracts was further subjected to gas chromatography-mass spectrometry. Qualitative determination of the different biologically active compounds from crude extracts of Silybum marianum using gas chromatography-mass spectrometry revealed different type’s chemical entities of high and low molecular weight of varying amounts present in each of the extracts. These chemical compounds are considered biologically and pharmacologically important. The study established the chemical composition and anticancer activity of the plant.