Objective: To evaluate the possible in vitro interaction between ethanolic extracts of Rhus coriaria (R. coriaria) (seed), Sacropoterium spinosum (S. spinosum) (seed), Rosa damascena (R. damascene) (flower) and certain known antimicrobial drugs including oxytetracycline HCl, penicillin G, cephalexin, sulfadimethoxine as sodium, and enrofloxacin. This synergy study was carried out against 3 clinical strains of multidrug-resistant Pseudomonas aeruginosa (P. aeruginosa). Methods: Evaluation of synergy interaction between plant extracts and antimicrobial agents was carried out using microdilution method. Results: The results of this study showed that there is a decrease in the MIC in case of combination of ethanolic plant extracts and test antimicrobial agents. The most interesting result was that the combination between R. coriaria and these antibiotics, showed a high decrease in minimum inhibitory concentration (MIC), and a strong bactericidal activity against these strains. Conclusions: These results may indicate that combinations between R. coriaria extract and these antibiotics could be useful in fighting emerging drug-resistance P. aeruginosa, which may due to that R. coriaria extract contain natural inhibitors working by different mechanisms or inhibiting efflux pumps. Now we have experiments underway leading to the identification of the active molecules present in R. coriaria. Further, in vivo experiments are needed to confirm pseudomonal protection.