Background: The aim in vitro study was to isolate and identify salivary mutans Streptococci and determine the ability of Green Tea Extracts and Nicotine to inhibit Growth, Biofilm Formation by salivary mutans streptococci. Materials and methods: This study included a convenient sample of 40 Iraqi volunteers aged 18–23 years old from College of Dentistry \University of Baghdad. Commercial green tea and nicotine were prepared in different concentration to use in agar diffusion method for detect the activity of extract, and ELISA reader in MTP was used to determine the ability of salivary mutans Streptococci to form biofilm in the presence / and absent of extracts.to measure the biofilm inhibition rate. Results: Mutans Streptococci were sensitive to green tea and nicotine in different concentrations the diameters of the inhibition zone were increase when the concentrations of the extracts increased. There was a significant difference between the concentrations of each concentration extracts, in their antibacterial activity, the MBC of green tea was (280 mg\ml). the MBC of nicotine was (45mg\ml). A recent study found that biofilm formation by mutans Streptococci was markedly decreased in the presence of 1\2 MBC of both green tea and nicotine with mean of O.D 590 nm = 0.54 in comparison with green tea extracts and nicotine alone O.D 590 nm = 0.15, 0.68 respectively. Conclusions: green tea and nicotine extracts in different concentration effectively reduced the biofilm formation of salivary M.S. While the presence of nicotine has negatively impacted on the ability of green tea extracts in the inhibition of biofilm formation by MS in vitro.