Abstract: New Guinea is one of the last remaining regions of extensive tropical forest and is an important biodiversity hotspot, yet most of its canopy ant species are poorly known. Here, we provide the first study of arboricolous ant communities of the genus Camponotus Mayr, 1861 from a lowland rainforest in New Guinea. We censused Camponotus nests in trees from two 0.32 ha forest plots in primary forest (389 trees) and secondary forest (296 trees) and explored their species diversity and nesting preferences. In total, 293 nests of 19 species were found. In 16 of the 19 species, major workers exhibited a set of morphological traits (i.e., flattened anterior part of head, swollen fore femora and maximal distance between frontal carinae greater than a third of head width) associated with phragmosis, an adaptation for arboricolous nesting. In primary forest, we detected 15 species in 124 nests versus only eight species in 169 nests in secondary forest. Only four species were shared between the two forest plots. Camponotus species differed significantly in their preferences for nesting microhabitats in both forest plots, ranging from species that were opportunistic and relatively abundant to those that specialized and nested only in living tree branches high in the canopy where they tended myrmecophilous scale insects. Of the 19 species collected, 13 are newly reported for New Guinea, including four that are described here as new species: Camponotus anezkae sp.n., Camponotus rotundus sp.n., Camponotus triangulatus sp.n. and Camponotus wanangus sp.n. In addition, Camponotus aruensis Karavaiev, 1933 is redescribed. Diagnostic features for species identification, digital photos of all available castes and morphological measurements are provided. The study demonstrates the high diversity of arboricolous Camponotus ants and their nesting habits within a single tropical forest site.