"It is with great joy that we welcome the appointment of Bishop Mafi to this leadership role in his Church," said Rev. Kioa.
"We congratulate our Tongan brother in Christ on this significant achievement."
Rev. Seforosa Carroll, UnitingWorld's Manager of Church Partnerships in the Pacific says the appointment is an important recognition of Tonga's contribution to the global Christian community.
"This is a timely acknowledgement of the energy and spirit of Christianity in the Pacific," said Rev. Carroll.
"Tongans are rightly renowned for their devotion to their Christian faith and worship. This is an appointment that all Pacific Christians can celebrate together."
The UCA's National Director of Multicultural and Cross Cultural Ministry Rev. Dr Tony Floyd has also warmly welcomed the appointment.
"Our Tongan community in Australia is a vibrant part of the Uniting Church and the wider Christian community," said Rev. Dr Floyd.
"We treasure and give thanks for the talents and gifts they exercise in sharing Christ's message across our Church and beyond."
"I hope Bishop Mafi's appointment will encourage members of our multicultural Church to share their gifts of ministry and leadership as well."