Japan and Tonga have agreed to a project which will see $US20 million granted to the upgrade and rebuild of Tonga's state broadcaster and the implementation of a disaster early warning system.
The aid was announced on the sidelines of the just-completed eighth Pacific Islands Leaders Meeting, or PALM, in Fukushima.
Tonga's Deputy Prime Minister Semisi Sika and Public Enterprise Minister Poasi Tei signed on Tonga's behalf.
Japan also granted Samoa a new aid package of $US1.8 million.
Announcing the Samoan aid, Japan Prime Minister Shinzo Abe said the money would go towards the provision of medical equipment in Samoa among other areas.
His Samoan counterpart Tuilaepa Sailele Malielegaoi co-chaired PALM and has been conferred the "Grand Cordon of the Order of the Rising Sun" by Japan.
This is in recognition to his long contribution to strengthening the relationship between Japan and Samoa, as well as between Japan and Pacific Island countries.