Bacterial infectious diseases continue causing havoc while pharmaceutical firms produce less inhibitor against pathogens. In the frame of this anti infectious fight, we chose to work on Lavandula multifida L. (Lm) from Southern Morocco. Steam-distillation of the plant was done with Clevenger-type apparatus and Essential Oil (EO) obtained was analyzed by gas chromatography (GC) and mass spectrometry (MS). A phytochemical study of the species was also performed through standard qualitative reactions with specific reagents. Antibacterial activity of EO was first achieved through discs-diffusion tests against Escherichia coli (Ec0A, Ec0B), Pseudomonas aeruginosa (Psa0A, Psa0B) and Klebsiella pneumoniae (Kp0A, Kp0B). Then Minimal Inhibitory Concentrations (MIC) were determined by macrodilution method and Minimal Bactericidal Concentrations (MBC) were determined. Steam-distillation of the species yielded 2.01 ml of EO for 100g of dried matter and analyses revealed Phenol 2,3,5,6 tetramethyl as major component with 89.97%. Phytochemical tests proved the existence of polyphénols, triterpenes, sterols, mucilage and saponosids. Biological tests proved that this EO has a significant antibacterial power against the germs despite their resistance to Beta-lactamin, aminosid and polymyxin antibiotics. Extreme inhibition diameters were 37.3±4.4mm for Ec0B and 10.6±0.5mm for Psa0A. 0.6µl/ml was the MBC against Ec0A, 9.6µl/ml was the MBC obtained against Psa0A and Psa0B. This study, among the rare found about this species, confirms its utilization by local people to treat digestive and respiratory infections. Discovery of a chemotype is a good way to valorize the species. It could be easily isolated to serve as a model for new antibacterial drug.