The present study was conducted to evaluate the biological activity of four Hypericum species, including H. perfoliatum L., H. aviculariifolium Jaup. and Spach subsp. depilatum (Freyn and Bornm.) Robson var. depilatum, H. origanifolium Wild. and H. linarioides Bosse, growing wild in Black Sea Region of Turkey. Ethanolic extractions of both flowers and leaves of Hypericum species were performed by maceration method. Total phenolic contents were ranged from 83.89 to 148.04 mg GAE/g for flower and 202.83 to 48.03 mg GAE/g for leaf extracts. Antioxidant activities of the extracts were determined between 8.63 – 39.35 mg trolox equivalent/g and the highest antioxidant activity was observed in H. linarioides extracts probably due to high phenolic content. Antimicrobial activities of the extracts were evaluated by minimal inhibitory concentrations (MIC) against seven Gram-positive and two Gram-negative bacteria. MIC results show that the flower extracts generally exhibited higher antimicrobial activity than the leaf extracts. The most prominent antibacterial activity was displayed by flower extract of H. perfoliatum (MIC between 4 – 512 µg/mL) and Escherichia coli was the most resistant organisms to all Hypericum species.