Red ginseng, made from the roots of Panax ginseng C. A. Meyer is used as a traditional medicine in East Asia to treat various diseases for more than 2000 years. Previously, we reported that red ginseng extract (RGE) containing more than90% ginsenosides might be a potential therapeutic agent for skin inflammation associated with atopic dermatitis (AD).Staphylococcus aureus in human skin microbiome has recently been known to be isolated with high frequency from patients with atopic dermatitis (AD). Thus, we examined whether RGE inhibits the production of virulence factors as an antibacterial activity against S. aureus, with the aim of applying it to the treatment of AD. RGE inhibited the expression of a/β/γ-hemolysin genes and the secretion of hemolysin toxin from S. aureus in dose-dependent manner. Next, since methicillin-resistant S. aureus (MRSA) is now commonly isolated from individuals with community-acquired infections, we examined how RGE affects antibiotic activity against MRSA. A minimum inhibitory concentration (MIC) assay revealed that RGE reduced the MIC values of b-lactam antibiotics and aminoglycoside antibiotics against two laboratory strains of MRSA by 0.03–0.25-fold. However, RGE did not alter the MIC values of fosfomycin, tetracycline, and erythromycin, suggesting that RGE acts selectively. RGE increases the bactericidal effect of antibiotics via a mechanism different from that used by triton X-100, which has been known to increases the antibacterial activity of b-lactam antibiotics. Therefore, RGE has the potential to be used as a very new antimicrobial agent for MRSA and/or S. aureus infection.