The purpose of this study was to determine the effectiveness of the methanol, acetone and chloroform extracts of three Hypericum (Hypericaceae) species (Hypericum pruinatum Boiss.&Bal., Hypericum olimpicum L. and Hypericum sabrum L.) against standard microorganisms, human pathogens, and methicillin-resistant Staphylococcus aureus strains isolated from clinical samples. Antimicrobial activities were conducted by using disc diffusion and broth microdilution methods. The strains were exposed to different plant extracts at concentrations ranging from 6.25 mg/ml to 0.003 mg/ml. It was determined that the chloroform extract of H. scabrum exhibited significant antimicrobial and anti- MRSA activity at doses ranging 3.125-0.0244 mg/ml against strains. The chloroform extracts of other plants had significant antimicrobial activities, too. Overall, the MRSA strains were more affected from extracts than standard microorganisms. Not only the H. olimpicum chloroform, H. pruinatum acetone, and H. scabrum chloroform extracts were determined as the most effective extracts against Streptococcus mutans strain at concentrations of 0.097 mg/ml, 0.195 mg/ml, and 0.195 mg/ml, respectively, but also they manifested good antifungal activity against Candida albicans at doses of 0.195 mg/ml, 0.195 mg/ml, and 0.0244 mg/ml, respectively. Consequently, it was revealed that Hypericum species, tested in this study, had significant antimicrobial and anti-MRSA activity and they may be a natural source of antimicrobial agents and may be used in the pharmacology industry.