The large wing part was brought to Canberra for analysis after it was found by locals on Pemba Island off the coast of Tanzania last month.
In a statement, Australia's Transport Minister Darren Chester said "it is highly likely that the latest piece of debris being analysed by the Australian Transport and Safety Bureau (ATSB) is from missing Malaysia Airlines flight MH370".
"The experts will continue to analyse this piece to assess what information can be determined from it," he added.
Australian officials have determined that four other pieces of debris found in Mozambique, South Africa and Mauritius almost certainly came from the plane, which was en route from Kuala Lumpur to Beijing when it vanished.
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But as hopes of finding MH370's final resting place fade after two years of searching, and with speculation that the crash zone may be slightly north of the search area, Chester defended the long-running and difficult underwater probe.
This "affirms the focus of search efforts in the southern Indian Ocean," he added.
Australia is leading the hunt for the missing plane in the southern Indian Ocean some 2,600 kilometres off its west coast capital of Perth after satellite data indicated the plane went down somewhere in that remote and stormy area.
As it stands, the combing of the 120,000 square kilometre search zone is expected to be finished by December, Chester added.
"We remain hopeful that the aircraft will be located in the remaining search area," he said.