The metre-long piece of metal, which had rivet holes along the edge and the number 676EB stamped on it, was found by 18-year-old Liam Lotter in December when he was walking on a beach in southern Mozambique, near the resort town of Xai Xai, authorities said on Friday.
Liam believed it belonged to an aircraft and brought it back to his home in South Africa.
His family, which dismissed it as a "piece of rubbish" that was probably debris from a boat, got in touch with the authorities when a suspected part of the missing airliner was found in Mozambique earlier this month.
"We are arranging for collection of the part, which will then be sent to Australia as they are the ones appointed by Malaysia to identify parts found," said Kabelo Ledwaba, spokesman of the South African Civil Aviation Authority.
Flight MH370 disappeared on March 8, 2014 en route from Kuala Lumpur to Beijing with 239 people on board.
A joint search in the South Indian Ocean, where the flight presumably had ended its journey, has yet to find the wreckage.
Last July, a two-metre-long aircraft flaperon was found on Reunion Island, which lies at the same corner of the Indian Ocean as Mozambique.
It was confirmed two months later by French investigators as belonging to the missing Malaysia Airlines plane.