Low pathogenic avian influenza virus (LPAIV) subtype H9N2 became latterly endemic in Egypt with major losses from complicated infections particularly with avian pathogenic Escherichia Coli (APEC) in commercial broilers. In the present study, forty broilers chickens were emerged into four equal groups (G1, G2, G3 and G4) where groups G1 and G2 vaccinated with LPAIV H9N2 vaccine at 7 days-old, while groups G3 and G4 act as non-immunized positive controls. By the day 28 of age groups G1 and G3 challenged with LPAIV H9N2 alone while groups G2 and G4 were co-infected with both H9N2 and E.Coli. LPAIV H9N2 Seroconversion, clinical picture, mortality record and virus shedding estimation via QrRT-PCR were all evaluated. The results revealed a significant mortality in co-infected groups G2 and G4 of 50% and 90% deaths respectively with severe clinical illness in compared to H9N2 infected groups only G1 and G3 with 0% and 20% mortalities respectively. Moreover, virus shedding was significantly elevated in co-challenged non-vaccinated group G4 followed by mono-infected non-immunized group G3 and the lesser significant detected viral load was in vaccinated H9N2 challenged group G1. In conclusion, the usage of H9N2 vaccines can significantly protect the broilers from mortality and minimize viral shedding post-challenge with H9N2 virus challenge only. Whereas, E.coli infection can precisely aggravate the virulence and pathogenicity of H9N2 when dually infected in terms of higher mortalities, inferior clinicopathological picture and elevated viral shedding even in vaccinated birds giving the necessity to control the secondary bacterial infection in broiler chicken flocks.