This study was designed to spot highlight on the incidence of fungal contaminants and Aflatoxins producing molds in 35 feed samples from 28 broiler and 7 egg-laying chicken flocks in Egyptian. Furthermore, the effects of feeding SPF-white Leghorn chicks on ration contaminated with 50 ppb Aflatoxin (AF) B1 on Newcastle Disease Virus (NDV)-Hemagglutination Inhibition (HI) antibody titers between the third and fourth weeks after vaccination with the live Hitchner B1 strain vaccine was investigated. The histopathological changes in liver, kidney,  bursae of Fabricius and spleen was performed at two and five weeks of exposure to AFB1. The most identified moulds were Aspergillus (94%), Penicillium (37%) and Fusarium (17%). The aflatoxigenic   A. flavus and A. parasiticus were isolated from (80%) and (9%) of feed samples, respectively. NDV-HI antibody titers were significantly (P< 0.05) decreased in AFB1 exposed group of vaccinated chickens than non-exposed group. The geometric mean titers of 4.9 log₂ and 5.7 log₂ were produced by sera of chickens group fed on normal ration while 3.9 log₂ and 3.8 log₂ were recorded by sera of chickens group fed on AFB1 contaminated ration 21 and 28 days post vaccination, respectively.  The results concluded that a significant (P< 0.05) increase in mean scores of the histopathological lesions exhibited by livers, kidneys and spleens of AFB1 exposed chickens in comparison with the non-AFB1 exposed chickens while, non-significant (P˃ 0.05) increase was detected for bursae of Fabricius respectively.