The ecoregion covers the lowland rain forests of New Britain, New Ireland, and nearby islands in the Bismarck Archipelago.

The ecoregion includes the lowland rain forests on New Britain, New Ireland, and nearby smaller islands, including Umboi, Long Island, and Karkar, near the New Guinea coast west of New Britain.

The islands are generally mountainous, with Mount Ulawun on New Britain reaching 2,334 m (7,657 ft).

These include the black honey buzzard (Henicopernis infuscatus), slaty-mantled sparrowhawk (Accipiter luteoschistaceus), New Britain sparrowhawk (Accipiter brachyurus), New Britain bronzewing (Henicophaps foersteri), blue-eyed cockatoo (Cacatua ophthalmica), green-fronted hanging parrot (Loriculus tener), Bismarck hawk owl (Ninox variegata), Bismarck kingfisher (Ceyx websteri), New Britain kingfisher (Todirhamphus albonotatus), rusty thicketbird (Cincloramphus rubiginosus), white-breasted monarch (Symposiachrus menckei), Matthias fantail (Rhipidura matthiae), black-bellied myzomela (Myzomela erythromelas), Ashy myzomela (Myzomela cineracea), scarlet-bibbed myzomela (Myzomela sclateri), mottled munia (Lonchura hunsteini), New Ireland munia (Lonchura forbesi), New Hanover munia (Lonchura nigerrima), and Bismarck woodswallow (Artamus insignis).

[6] A 2017 assessment found that 1,026 km2 (396 sq mi), or 3%, of the ecoregion is in protected areas.