Vodafone Fiji will take over management of Papua New Guinea's mobile phone carrier BeMobile.
The deal was announced by the two countries' prime ministers, Peter O'Neill and Commodore Frank Bainimarama in Port Moresby.
The plan will see the Vodafone brand brought to PNG and the Solomon Islands.
Fiji's National Provident Fund will take a 40 per cent share of BeMobile, while the PNG government's commercial arm, the Independent Public Business Corporation, will take 51 per cent.
The remaining nine per cent of shares will be spread between the PNG Sustainable Development Program and superannuation providers Nambawan Super, Nasfund and GEMS.