The galls of Quercus infectoria are commonly used in Malay traditional medicine to treat wound infections after childbirth. In India, they are employed traditionally as dental applications such as that in treatment of toothache and gingivitis. The aim of the present study was to evaluate the antibacterial activity of galls of Quercus infectoria Olivier against oral bacteria which are known to cause dental caries and periodontitis. Methanol and acetone extracts were screened against two Gram-positive bacteria (Streptococcus mutans ATCC 25175 and Streptococcus salivarius ATCC 13419) and two Gram-negative bacteria (Porphyromonas gingivalis ATCC 33277 and Fusobacterium nucleatum ATCC 25586). The screening test of antibacterial activity was performed using agar-well diffusion method. Subsequently, minimum inhibitory concentration (MIC) was determined by using twofold serial microdilution method at a concentration ranging between 0.01 mg/mL and 5 mg/mL. Minimum bactericidal concentration (MBC) was obtained by subculturing microtiter wells which showed no changes in colour of the indicator after incubation. Both extracts showed inhibition zones which did not differ significantly (P < 0.05) against each tested bacteria. Among all tested bacteria, S. salivarius was the most susceptible. The MIC ranges for methanol and acetone extracts were the same, between 0.16 and 0.63 mg/mL. The MBC value, for methanol and acetone extracts, was in the ranges 0.31–1.25 mg/mL and 0.31–2.50 mg/mL, respectively. Both extracts of Q. infectoria galls exhibited similar antibacterial activity against oral pathogens. Thus, the galls may be considered as effective phytotherapeutic agents for the prevention of oral pathogens.