Antibiotic resistance of Klebsiella pneumoniae (K. pneumoniae) has become alarming to public health, moreover biofilm production is one of the virulence mechanisms that contributes to antibiotic resistance. Metal oxide nanoparticles are showing promise as antibacterial agents. The purpose of this study was to assess the antibacterial activities and dosage effect of ZnO-NPs against ESBL K. pneumoniae isolates recovered from horses exhibiting respiratory symptoms. The antibiotic sensitivity of ESBL producing K. pneumoniae strains was tested using the Kirby Bauer disc diffusion method, which showed 100% resistance to cefotaxime and erythromycin while resistance to tetracycline, ampicillin, amoxicillin / clavulanic acid, ceftriaxone, ceftazidime, amikacin and ciprofloxacin were 85.7, 71.42, 42.85, 28.57, 28.57, 14.28 and14.28%, respectively. Regarding the biofilm production genes scanning, K. pneumoniae isolates were positive for luxS gene (100%), while only 85.7% of K. pneumoniae were positive for Uge gene and none of them having mrkD gene. ZnO-NPs were tested against a local isolate of ESBL-producing K. pneumoniae for their antibacterial properties. K. pneumoniae had MIC and MBC values of 5ug/ml and 3ug/ml, respectively. In the current study, antibiotic abuse leads to an increase in the population of ESBL-producing K. pneumoniae, posing a concern to public health. ZnO-NPs, a new material, exhibit significant antibacterial activity against hypermucoviscosity K. pneumoniae isolate.