Background and Objectives: Expressions of lasA and lasB genes of Pseudomonas aeruginosa are associated with bacteri- um pathogenicity. The present study was aimed to assess the effect of Satureja khuzistanica essential oil (SKEO) extract on expression of lasA and lasB genes in P. aeruginosa. Materials and Methods: Pseudomonas aeruginosa isolates were cultured in Mueller Hinton broth containing sub-inhibi- tory concentrations of SKEO and total RNA extracted using Trizol method. cDNA was synthesized using random Hexamer primer and finally the expression of lasA and lasB genes carried out by real-time PCR. Results: The MICs of SKEO extract for PA9, PA10, PA11, PA13, PA41 and PA42 isolates were 8, 8, 8, 9, 7 and 12 µg/ml, respectively. Statistical analysis for 6 isolates revealed that the reduction in expression of lasA and lasB genes under SKEO treatment was significant (P<0.05). Conclusion: The insignificantly increasing of lasB gene expression may lead to low virulent strains, for probably reason that the strain’s exotoxin A are destroyed in the high amount of protease. In conclusion, using of SKEO in burned patients infected with P. aeruginosa may be effective; however, it is better to assess the spectrum activity of SKEO, pharmacokinet- ics, potency and its toxicity in human cells.