We report new observational and specimen data on the avifauna of Kolombangara, Western Province, Solomon Islands. These data, collected from 3–9 October 1974 and 13–21 May 2004, and supplemented with more recent observations, represent the first comprehensive survey of this globally significant island since 1927. All encounters of montane species are reported along with select species accounts for notable lower-elevation species. Numerous observations presented here suggest avifauna even more unique than previously reported. For example, we confirm a probable resident form of Peregrine Falcon (Falco peregrinus) and report the first observations and collected materials for a Blue-faced Parrotfinch (Erythrura trichroa) from Kolombangara. We observed all of the island's high-elevation endemics and found their relative abundances and patterns of occurrence to be consistent with those of an intact montane avifauna. Our findings suggest that despite large-scale modification of lowland habitat, montane forests on Kolombangara still maintain the full complement of endemic and other high elevation species described nearly 100 years ago, along with several additional taxa not previously recorded. However, incidental evidence suggests that forest change in the lowlands is impacting montane microclimates as indicated by extensive drying of epiphytic mosses at high elevations. Along with more recent collection of undescribed anurans, these findings confirm the global conservation significance of the montane forests and biodiversity on Kolombangara.