The Islands of East Melanesia have a unique and highly endemic frog fauna derived entirely from overseas colonisation events. Within East Melanesia New Britain is a notable centre of frog diversity and endemism, with at least 15 endemic species, mostly in the ceratobatrachid genus Cornufer. Here we describe the first endemic pelodryadid treefrog from New Britain. The new species is a member of the Litoria thesaurensis species group but can be distinguished from near relatives by aspects of body size, webbing extent, bone pigmentation and male advertisement call. The two known specimens of the new species were collected in Hill Forest on karst basement in the Nakanai Mountains in East New Britain. The new species provides new evidence of diversification of insular PelodrydidaePelodrydidae, and reinforces New Britain, and especially the predominantly karst Nakanai mountains, as a hotspot of frog diversity in East Melanesia. In light of high rates of forest loss and conversion New Britain is also a region of significant conservation concern.