Previous study had shown that teak leaves have antibacterial compounds such as flavonoid, fenolic, tannin, and quinnones. The purposes of this research was to determine the inhibitory of those antibacterial compounds in teak leaves extract through well-diffusion method for pathogenic bacteria such as Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Teak leaves extract was concentrated to 5, 10, 15, 20, and 25% for the well-diffusion method. The selected extract concentration was proceeded to the stability test toward pH, salt, sugar, and heat. In addition, toxicity test was also performed to the selected teak leaves extract. The results showed that teak leaves extract could inhibit the growth of the bacteria by the presence of inhibitory diameter, Bacillus subtilis (12.03±1.220mm to 16.91±0.707mm), Staphylococcus aureus (12.76±1.529mm to 18.34±0.884mm), Pseudomonas aeruginosa (11.93±0.345mm to 16.79±0.115mm), and Escherichia coli (10.64±0.371mm to 18.19±0.168mm). However, the stability of the extract is not too stable that is indicated from the decreased inhibitory diameter. The result of toxicity test of the teak leaves extract is slightly toxic.