Career diplomat Brett Aldam is to become Australia's next High Commissioner to Tonga, Foreign Minister Bob Carr has announced.

Mr Aldam is set to replace Thomas Roth in the Pacific island's capital, Nuku' Alofa, next month.

Senator Carr says Mr Aldam is a career officer with the Department of Foreign Affairs and Trade and was Australian High Commissioner to the Republic of Kiribati until June 2012.

He has previously served as deputy head of mission at the Australian High Commission in Nairobi, Kenya and as third secretary at the Australian High Commission in Suva, Fiji.