In this study, we investigated which structural proteins of pigeon paramyxovirus type 1 (PPMV-1) are responsible for its low pathogenicity in chickens. The results revealed that the pathogenicity of the virus is determined by multiple genes. The NP protein and F protein were found to have the strongest individual effect on virulence, and this effect further enhanced when the two proteins were expressed in combination. Our study highlights the influence of the NP and F proteins on the pathogenicity of PPMV-1 in chickens.