The Northwest Solomonic Austronesian languages of Bougainville and the western Solomon Islands display numerous linguistic characteristics that are atypical of other Austronesian languages of the Oceanic subgroup. These innovative features have been assumed to reflect linguistic contact with the Papuan languages of the region. However, while contact-induced change resulting from social contact between speakers of Austronesian and Papuan languages has been shown to play a significant role in the history of a number of languages and groups of languages in Melanesia, there has been little detailed research on the Northwest Solomonic subgroup. The Mono-Uruavan languages (Mono, Uruava, and Torau), a subgroup within Northwest Solomonic, are particularly aberrant with regard to grammatical structures. They display right-headed structures including SOV clauses, postpositions, and preposed possessors. We argue that these innovative structures arose through Mono-Uruavan speakers' social contact with speakers of neighboring Papuan languages of the South Bougainville family (Nasioi, Nagovisi, Buin, Motuna).