The two horns, believed to have come from Africa and worth an estimated USD 365,000, were found hidden in the luggage of a passenger who arrived in Ho Chi Minh City on a flight from Doha on Sunday, the southern city's Phap Luat newspaper reported.
The Vietnamese passenger has been taken into police custody for investigation, the report said, without specifying whether the man had been officially arrested.
Illegal hunting of rhinos has risen in recent years to meet surging demand for their horns in parts of Asia, in particular Vietnam where they are highly prized for their supposed medicinal qualities.
At a major CITES meeting in March, Hanoi was asked to develop a database to track legal rhino horn trophies and to reduce local demand for the substance.