Antiseptic application on cow’s teat after milking is essential to prevent the udder infection during milking. This study aimed to evaluate the antibacterial effectiveness of Tectona grandis leaves extract as the main ingredient of antiseptic gel for cow’s teat as the innovation from conventional antiseptic solutions. The effects of herbal gel antiseptic on milk quality and the level of mammary inflammation (mastitis) were also determined. The mammary inflammation level determined by California Mastitis Test (CMT). Total of four sub-clinical mastitis cows (sixteen teats) were used in the completely randomized design split plot in time (four treatments and four replications). The main plots were the red teak leaves extract with different levels: 0.10% (P1); 0.06% (P2); 0.02% (P3) and povidone iodine (P0) as positive control. The sub-plot was the duration of treatments (0, 5 and 10 days). The result showed that bacterial counts in milk from cows using herbal antiseptic gel (P1, P2, P3) were lower (P<0.05) than those using povidone iodine (P0). The bacterial counts in milk and the mammary gland’s inflammation degree were significantly decreased (P<0.05) as the treatment duration increased. There were significantly difference on the level of mammary inflammation healing between cows using herbal antiseptic gel and povidone iodine. The decreased level of mammary inflammation was thought to have an effect on increasing the protein, fat, and lactose contents in milk of cows using herbal gel (P<0.05). Hence, the antiseptic gel with the lowest dose (0.02%) has the potential for use as anti-inflammatory agents.