In this study, the antibacterial activity of Sideritis curvidens Stapf. and Sideritis lanata L. were investigated. The antibacterial effects of the essential oils, which were obtained from voucher specimens of the plants by the hydrodistilled method, were tested by a disk diffusion method using Streptococcus mutans CNCTC 8/77, Staphylococcus aureus ATCC 6538 P, Staphylococcus aureus MU 38, Staphylococcus epidermidis MU 30, Micrococcus luteus NRRL B-4375, Bacillus subtilis ATCC 6633, Bacillus cereus RSKK 863, Escherichia coli ATCC 11230, Escherichia coli ATCC 35218, Pseudomonas aeruginosa ATCC 27853, Shigella sonnei RSKK 878, Enterobacter aerogenes RSKK 720, and Salmonella typhimurium CCM 5445. Both essential oils showed similar potencies against all tested microorganisms. The results showed that the essential oils of Sideritis curvidens Stapf. and Sideritis lanata L. had a strong antimicrobial effect against Gram-positive bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA) and oxacillin-resistant coagulase negative Staphylococcus epidermidis. In additional, B. cereus, B. subtilis, and M. luteus were found as the most sensitive bacteria to essential oils of Sideritis curvidens Stapf. and Sideritis lanata L., and both essential oils were more effective against these bacteria than the reference antibiotics used in this study.