BS endophytic fungus is a fungus isolated from the flower of the bitter plant (A. paniculata) which is known to produce various secondary metabolites which are reported to have antibacterial bioactivity. The purpose of study aims to determine the antibacterial activity of endophytic BS extract isolated from bitter flowers (A. paniculata) on brown rice growing media against Streptococcus mutans, Staphylococcus aureus, and Pseudomonas aeruginosa bacteria. BS endophytic fungi were grown on brown rice media and then extracted by maceration method with ethyl acetate as solvent. The antibacterial activity test of the extract was carried out by disc diffusion method. The results showed that BS endophytic mushroom extract grown on brown rice media could inhibit' the growth of Streptococcusi 'mutans, Staphylococcus aureus, and Pseudomonas aeruginosa bacteria, at concentrations of 10%, 30%, and 50%. In conclusion, BS endophytic fungus isolated from A. paniculata flower can inhibit the growth of bacteria with the smallest diameter inhibitors successively on Staphylococcus aureus, Streptococcus mutans, Pseudomonas aeruginosa bacteria.