This work evaluated the bactericidal activity and determinated the Minimum Inhibitory Concentration(MIC) of ethanolic extract and essential oil from Rosmarinus officinalis L. leaves on microorganisms ofinterest in food industry: Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Shigella sonnei,Listeria monocytogenes, Pseudomonas aeruginosa, Bacillus cereus and Lactobacillus plantarum. The essential oilshowed a broad spectrum of antimicrobial action for both Gram positive and Gram negative bacteriawith MICs between 512 - 4096 ppm. The ethanolic extract showed antimicrobial activity against S.sonnei, S. typhimurium and L. monocytogenes with a MIC of 1024 ppm. Nisin was used as positive controland showed a strong growth inhibition of all bacteria tested with MICs between 2 and 1024 ppm. Ourresult shows that preservatives commonly used in the food industry have lower antimicrobial activitythan those found in essential oil from R. officinalis L. leaves.