Transmission of avian viruses both bird-to-bird and from birds to non-avian species is a major health concern. Newcastle disease virus (NDV) is an economically important avian virus that poses substantial risks to the poultry industry. Rapid and sensitive diagnostic methods, such as the enzyme-linked immunosorbent assay (ELISA), are required to track such infections. To develop an ELISA for detecting anti-NDV antibody in avian sera, the nucleocapsid protein (NCP) gene of the NDV La Sota strain was cloned and expressed in Escherichia coli and the 513-amino acid recombinant NCP was purified by Ni-NTA affinity chromatography. To evaluate its ability to replace NDV whole virus antigen as a coating antigen, NCP-coated and whole NDV-coated ELISAs were tested and compared using a panel of NDV positive antisera from chickens. Results using purified NCP were highly correlated with those obtained using whole NDV (r=0.927), demonstrating that recombinant NCP expressed in Escherichia coli is a suitable substitute antigen for whole NDV in a diagnostic ELISA.