Background: The pharmacological efficiency of herbal drugs has shown to be effective as conventional pharmaceutical drugs. Preliminary screening of herbal extracts helps in analysing the bioactive compounds present. Ocimum sanctum, the queen of herbs keeps a spiritual importance in Indian culture and have important place in traditional medicinal system of India. Objectives: The present study was implement to investigate the preliminary phytochemical screening and GC-MS analysis of leaf extract of O. sanctum to determine the phytoconstituents. Materials and Methods: Leaves collected were dried, crushed and mixed with ethanol and water and further applied for extract preparation. The prepare extract was used for phytochemical and GC-MS analysis. Results: In qualitative phytochemical analysis tannins, carbohydrate, quinine, anthraquinones, coumarins, phlobatanins, alkaloids, flavonoids, glycosides, terpenoids, diterpenes, phenols were found present while GCMS analysis showed Eugenol, Cyclohexane, bicyclo[7.2.0]undec-4-ene, 4,11,11-trimethyl-8-methylene, Oxatricyclo[ 22.214.171.124(4,6)]dodecane,,12-trimethyl-9-methylene, Tetracontane, Phytol were present in majority. Conclusion: The study concluded that O. sanctum leaf extracts contain many biological active compounds which could be exploited for a development of plant based drug.