Announcing the deal along with Boeing at the final trade day of the Singapore Airshow, Air Niugini chairman Sir Frederick Reiher said the carrier needed the planes "urgently".
The airline currently has a domestic service, as well as flights to Australia, Singapore, Fiji, the Philippines, Solomon Islands, Hong Kong, Vanuatu and Japan. It is planning to fly to China in the near future.
Dinesh Keskar, regional senior vice president for sales at Boeing Commercial Airplanes, said the aircraft had its first test flight in late January and was "performing exceptionally well".