Acanthopanax (A.) henryi (Oliv.) Harms contain many bioactive compounds commonly used in traditional Chinese medicine. The objective of the present study was to investigate the antibacterial activity of the single constituent, Eleutheroside K (ETSK) isolated from the leaves of A. henryi (Oliv.) Harms, against methicillin‐resistant Staphylococcus (S.) aureus (MRSA). Broth microdilution assay was used to measure the minimal inhibitory concentration (MIC) and the MIC values of ETSK against eight clinical S. aureus strains were all 50 µg ml−1. At sub‐inhibitory concentrations, a synergistic effect between oxacillin (OXA) and ETSK was confirmed using checkerboard dilution assay and time‐kill curve analysis. The bacteriostatic effect became more pronounced when ETSK was used in combination with detergent (Triton X‐100) or ATPase inhibitor (N, N′‐dicyclohexylcarbodiimide). According to western blot analysis, the down‐regulated expression of Penicillin‐binding protein 2a (PBP2a) further validated that the bacterial activity was inhibited when treated with ETSK in a dose‐dependent manner. Results based on our study verified that ETSK significantly suppressed MRSA infections and emphasized the potential application of ETSK as a novel anti‐MRSA natural drug. Significance and Impact of the Study: The growing emergence of multidrug‐resistant bacteria represent a formidable challenge to worldwide public health. In response to this intractable issue, we were committed to investigate the antibacterial activity of Eleutheroside K (ETSK) isolated from Acanthopanax (A.) henryi (Oliv.) Harm. The results showed that ETSK can effectively inhibit the growth of methicillin‐resistant Staphylococcus (S.) aureus (MRSA). Furthermore, the synergistic effect between ETSK and β‐lactam antibiotic revealed that ETSK could reverse the methicillin resistance of S. aureus. The present study provided the experimental basis for application of ETSK as a novel therapeutic approach in MRSA infections.