Objectives: Newcastle disease (ND) is a serious contagious disease that may cause up to 100% mortality in poultry. Whereas vaccination is one of the only safeguard against endemic ND and the conventional vaccines are not heat stable and therefore require complex cold-chains to link the vaccine producers and users, the aim of this study was to evaluate the efficacy of thermostable ND vaccine strain I-2 in broiler chickens vaccinated via drinking water and coated on oiled wheat grain. The horizontal transmission of vaccine virus and transmission of disease were also evaluated. Materials