Newcastle disease virus (NDV) is an avian virus belonging to the family Paramyxoviridae and the causative agent of Newcastle disease. The desire to study NDV is due not only to the significant economic impact it has on the poultry industry worldwide, but also its potential use as an oncolytic agent and vaccine vector for human and animal use.^1-3 Of great importance to NDV is the attachment surface glycoprotein, haemagglutinin-neuraminidase (HN). HN recognises and binds sialylated structures on host cells and facilitates virus-cell membrane fusion. It has been shown that the N-linked glycans present on HN can modulate the ability of the virus to infect cells and stimulate the host immune system.⁴ However, characterisation of site-specific glycan occupancy and heterogeneity remains one of the few unexplored areas related to NDV HN. Accordingly, mapping the repertoire of glycans from HN may help elucidate mechanisms of infectivity and immune evasion. Not only with respect to NDV, but also within closely related viruses that cause disease in humans, such as parainfluenza viruses. Liquid chromatography-MS/MS strategies were implemented to structurally characterise the digested glycoprotein. Dissociation techniques included higher collision energy dissociation (HCD) and electron transfer dissociation (ETD) using high mass accuracy Orbitrap mass analysis and collision induced dissociation (CID) with linear ion trap mass analysis. Examination of NDV HN revealed considerable diversity amongst the N-linked structures, with up to sixty-three glycoforms present at one site. These included high mannose, fucosylated, sialylated and mono- and disulphated N-linked glycans. In addition, a novel sialylated O-linked glycan was also discovered, which may have implications in the functional interactions of the protein.