A comprehensive review of the morphology, anatomy, taxonomy, chemistry and ecology of the endemic New Zealand facultative shrub epiphyte Pittosporum cornifolium (Pittosporaceae) is presented. Strong habitat specificity restricts this species to lowland forest and coastal habitats, which are widely yet discontinuously distributed north of latitude 42°15′S. Pittosporum cornifolium is typically associated with old growth forest systems and low nutrient substrates, with low mean daily temperatures in the coldest month (<0.6 °C) and high mean October vapour pressure deficits (>0.5 kPa) apparently restricting its distribution. Significant morphological variability is evident in leaves and flowers, especially with respect to plants from the Poor Knights Islands. Genetic analyses of five mainland populations and individuals representing Poor Knights Islands populations revealed relatively low genetic diversity at the population level which is likely to be the result of geographic isolation. Molecular phylogenetic studies suggest a New Caledonian origin for the species with close affinities to both P. pimeleoides subspecies. Several lines of evidence suggest recognition of the Poor Knights Islands entity as a new taxon. However, analysis of additional morphological, reproductive and molecular data across the full geographic range will be required to confirm current inferences. Although populations have declined, P. cornifolium is not currently threatened, however, it should be considered for reintroduction to sites in districts where its range has been severely reduced.