Background:Plant-derived compounds have action alongside Gram-positive and Gram-negative bacteria and numerous compounds, inhibit efflux pumps and hence have become known as efflux pump inhibitors. Clarithromycin is a macrolide antibiotic used to treat pharyngitis, tonsillitis, acute maxillary sinusitis and acute bacterial exacerbation of chronic bronchitis the antibacterial range is the similar as erythromycin but it is active against Mycobacterium avium complex, M.leprae and atypical mycobacteria. The in vitro antibacterial activity results of different boswellic acid compounds discovered alpha keto-boswellic acid (AKBA) to be the preponderance potent antibacterial compound alongside Grampositive pathogens, but it showed no significant antibacterial activity (MIC >128 μg/ml) against the Gram negative bacteria . Aim: The aim of present study, is to illustrate the effectiveness of Boswellia carteri against Gram positive and negative bacteria alone and in combination with clarithromycine to elucidate the synergestic antibacterial effects and how Boswellia carteri modifying the antibacterial activity of clarithromycine. Material and methods: The bacteria strains used in this study included five Gram-positive bacteria (Staphylococcus aureus, Streptococcus faecalis, Bacillus cereus, Staphylococcus epidermidis, Staphylococcus saprophyticus) and three Gramnegative bacteria (Klebsiella pneumoniae and Escherichia coli and Pseudomonas aeruginosa) five for each strains. Antibacterial activities were evaluated by measuring inhibition zone diameters by Agar-well diffusion ,while Broth dilution method determine MIC .Then fractional inhibitory concentration determine the in vitro interaction of clarithromycine and boswellia carteri combination. Results :The result of present study showed that zone of inhibition of clarithromycine ranged from 4mg/ml for Pseudomonas aeruginosa and 19mm toward Klebsiella pneumonia while zone of inhibition of Boswellia carteri ranged from 6mmfor Pseudomonas aeruginosa to 14mm for Klebsiella pneumonia the p value was insignificant p ?0.05 but the combined mixture showed significant differences from either clarithromycine or boswellia carteri p ?0.05. The MIC ranged from 8-32mg/ml,8-64mg/ml and 8- 16mg/ml for clarithromycine, boswellia carteri and combined clarithromycineand boswellia carteri respectively and the Fractional inhibitory concentration of the combined mixture is more potent than clarithromycine and boswellia carteri alone. Conclusions Boswellia carteri produced valuable property when combined with clarithromycine for sensitive bacteria and as a result others studies desirable for in vivo synergistic studies.