The essential oil from the aerial parts of Marrubium incanum Desr. (Lamiaceae), obtained by hydrodistillation, was analyzed by GC and GC-MS. Forty-six compounds were identified, representing 96.3% of the total oil. The main components of the oil were (E)-caryophyllene (27.0%), germacrene D (26.2%) and bicyclogermacrene (11.5%). The microbial growth inhibitory properties of the isolated essential oil were determined using the agar diffusion and broth microdilution method against seven bacterial species (Staphylococcus aureus ATCC 25923, S. epidermidis ATCC 12228, Micrococcus flavus ATCC 10240, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Klebsiella pneumoniae NCIMB 9111, and Pseudomonas aeruginosa ATCC 27853), and two strains of the yeast Candida albicans (ATCC 10259 and ATCC24433). The essential oil showed activity against all the microorganisms tested, but differences in microbial susceptibility were registered.