The chemical composition and the antimicrobial potency of four Satureja essential oils (EOs), and their synergism with two antimicrobials have been investigated. Gas chromatography (GC) and GC/mass spectrometry analysis showed that S. alpina EO was predominated by pulegone (88.8%), while pulegone (38.6%) and menthone (30%) were the major constituents of S. calamintha EO. S. montana and S. hortensis EOs were dominated by carvacrol (50.8%-32.8%), γ-terpinene (18.5%-40.1%), and p-cymene (8.2%-7.3%), respectively. The antimicrobial activity showed that S. montana and S. hortensis EOs exhibited potent activity (minimal inhibitory concentration and minimum microbiocidal [bactericidal and candidacidal] concentrations = 0.07-4.46 mg/mL for bacteria, and 0.27-1.11 mg/mL for Candida). All EOs showed high synergism with gentamicin against bacteria (gains ranged between 4- and 512-fold). Interestingly, this synergism was pronounced against the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. Regarding the association with amphotericin B, synergistic and additive effects were recorded depending on the strain tested.