PA 1874 is an efflux pump with a role in the antibiotic resistant mechanism among Pseudomonas aeruginosa especially biofilms. This work aimed to detect the biofilm formation and its effect on antibiotic susceptibility pattern of P. aeruginosa isolated from clinical samples, and to measure the expression of PA1874 gene among P. aeruginosa isolates. This study was conducted on 64 P. aeruginosa isolates. Biofilm was measured using tube method. Antibiotic susceptibility of nonbiofilms and biofilm +ve isolates and planktonic counterparts for ciprofloxacin, tobramycin and gentamycin was tested using tube microdilution method. Expression of PA1874 gene was measured using Syper green real time PCR. We found that 26 isolates (40.6%) were biofilm +ve.The biofilm formation was statistically significant high among endotracheal tube aspirate and urine isolates. None of biofilm forming isolates were susceptible to the 3 antibiotics compared to the presence of some susceptible isolates among the planktonic counterpart and non-biofilms. In biofilm isolates, expression of PA1874 gene was significantly high in biofilm cells more than planktonic counterpart and non biofilms. We concluded that P. aeruginosa has high ability of biofilm formation that may be the main cause of antibiotic resistance especially in isolates from artificial devices as urinary catheters and endotracheal tubes and PA1874 gene expression is an important mechanism of resistance in P. aeruginosa biofilm