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The potential antibacterial activity of basil (<i>Ocimum basilicum</i>), chamomile (<i>Matricaria chamomilla</i>), origanum (<i>Thymus capitatus</i>), tea tree (<i>Melaleuca alternifolia</i>) and thyme (<i>Thymus vulgaris</i>) essential oils, was investigated against 29 Gram-positive bacterial strains isolated from wastewater treatment plants, clinical samples (n = 25) and American Type Culture Collection (ATCC) reference strains (n = 4). Wild bacterial strains included methicillin-resistant <i>Staphylococcus aureus</i> (n = 16) and vancomycin-resistant <i>Enterococcus</i> spp. (n = 9). The antimicrobial activity of the selected oils was studied using the broth macrodilution method. The Minimal Inhibitory Concentration (MIC) values for <i>S. aureus</i> ranged from 0.06 to 0.5% (<i>v/v</i>) for origanum oil, 0.06 to 1% (<i>v/v</i>) for thyme oil, 0.12 to 1% (<i>v/v</i>) for tea tree oil, 0.25 to 4% (<i>v/v</i>) for basil oil and 2 to &gt;4% (<i>v/v</i>) for chamomile oil. For enterococci the MIC values were significantly higher ranging from 0.25 to 1% (<i>v/v</i>), 0.5 to 2% (<i>v/v</i>), 1 to 4% (<i>v/v</i>), 4 to &gt;4% (<i>v/v</i>) and &gt;4% (<i>v/v</i>) for the above-mentioned oils, respectively. The main compounds of the tested essential oils were: estragole (<i>Ocimum basilicum</i>), bisabolol and trans-b-farnesene (<i>Matricaria chamomilla</i>), carvacrol and thymol (<i>Thymus capitatus</i>), terpinen-4-ol and p-cymene (<i>Melaleuca alternifolia</i>), thymol, linalool, and p-cymene (<i>Thymus vulgaris</i>). Origanum essential oil yielded the best antimicrobial results followed by thyme, tea tree, and basil oil, while chamomile oil exhibited weak antibacterial properties.