A new species is described from New Caledonia in the genus Goniothalamus, which now includes three endemic species from the archipelago. The new species was first collected over 150 years ago, but had not been subsequently studied until now. Material of the New Caledonian taxa was included in a recent molecular phylogeny, which shows that they are related and belong to the same clade, but they are easily distinguished from one another by morphology. Goniothalamus hmoope sp. nov. differs from G. obtusatus by its smaller leaves and its monocarps that are terete and 3-8 seeded (vs narrowly ellipsoid, ellipsoid, subglobose to obovoid, 1-3-seeded), and from G. dumontetii by its flat leaves with plane secondary veins (versus slightly bullate with impressed venation), and its monocarps that are terete (vs flattened elongate with lateral triangular projections). The new species, which is restricted to the North Province and can be abundant in the Mt. Panié range, was assessed by the New Caledonian Red List Authority as Vulnerable (VU) based on the IUCN Red List criteria.