A total of 150 samples collected from freshly dead chickens were examined for Coliform bacteria. The results revealed isolation of 141 isolates (84 E. coli (56%), 6 Klebsiella pneumoniae (4%), 10 Klebsiella oxytoca (6.6%), 17 Klebsiella ozanae (11.3%), and 24 Citrobacter freundii (16%)). Strong biofilms on Congo red agar were produced by 37 E. coli isolates (44%), 3 Klebsiella pneumoniae (50%), 5 Klebsiella oxytoca (50%), 7 Klebsiella ozanae (41%) and 10 Citrobacter freundii (41%). Antimicrobial susceptibility test on strong biofilm producer isolates revealed that all isolates exhibited high resistance to amoxicillin, oxytetracycline and erythromycin, trimethoprim sulfamethoxazole, while their sensitivity to gentamicin was high. Strong biofilm E. coli isolates were serotyped to O91:H21, O17:H18, O78, O114:K90, O26:K60, O121:H7, O128:H2, O113:H4, O159, O44:K74 and O55:K59. Klebsiella pneumoniae serotypes wereK1 and K2. Zinc oxide nanoparticles were45.86 ± 45.71 nm in size, 0.223 ± 0.149 PDI and zeta potential -14.2 ± 1.68 mv, while Propolis-NPs had particle size 291.6 ± 23.32 nm, 0.351 ± 0.026 PDI and zeta potential -9.88 ± 2.53 mv. SRB cytotoxicity assay showed that the highest concentration of propolis-NPs (75%) caused 88.88% cell viability, while ZnO-NPs showed cell viability more than 95% untill17.5 µg/ml. ZNO-NPs MIC was 35µg/ml for all coliform isolates. Its antibiofilm effect was observed at concentrations 8.75 and 17.5µg/ml for both E.coli and Citrobacter freundii, while Klebsiella species biofilm formation was inhibited at 17.5 µg/ml ZNO-NPs. Moreover Propolis-NPs MIC against all tested isolates was 37.5% while antibiofilm activity was detected at 18.75%.