BACKGROUND There has been a great interest in developing strategies for enhancing antigen delivery to the mucosal immune system as well as identifying mucosal active immunostimulating agents. To elevate the potential of O-2'-Hydroxypropyl trimethyl ammonium chloride chitosan (O-2'-HACC) as an adjuvant and mucosal immune delivery carrier for DNA vaccine, we prepared the O-2'-HACC loaded with Newcastle disease virus (NDV) F gene plasmid DNA and C3d6 molecular adjuvant (O-2'-HACC/pFDNA microparticles). RESULTS The O-2'-HACC/pFDNA exhibited a regular spherical morphology with a particle size of 202.3 ± 0.52 nm, a zeta potential of 50.8 ± 8.21 mV, encapsulation efficiency of 90.74 ± 1.10%, and a loading capacity of 49.84 ± 1.20%. The plasmid DNA could be sustainably released from the O-2'-HACC/pFDNA after an initial burst release. Intranasal vaccination of chickens immunized with O-2'-HACC/pFDNA not only induced higher anti-NDV IgG and sIgA antibody titers but also significantly promoted lymphocyte proliferation and produced higher levels of IL-2, IL-4, IFN-γ, CD4+, and CD8 + T lymphocytes compared with the NDV commercial live attenuated vaccine. Intranasal delivery of the O-2'-HACC/pFDNA enhanced humoral, cellular, and mucosal immune responses and protected chickens from the infection of highly virulent NDV compared with the intramuscular delivery. CONCLUSIONS Collectively, our findings indicated that the O-2'-HACC could be used as a vaccine adjuvant and delivery system for mucosal immunity and have an immense application promise.