The Tuoi Tre newspaper and news portal tuoitrenews.vn reported that Huong had said she was given the soap as a gift by a woman, identified only as Helen, while they were on a trip to the coastal city of Vung Tau.
Huong told the court she wanted to take them to Australia as gifts and was not aware of what they contained.
However, the Ho Chi Minh City Police newspaper, controlled by the city's police, said Huong had failed to prove that the other woman was real.
The court ruled that the offence was "extremely dangerous to the community" and found her guilty. She now faces death by lethal injection.
Huong has 15 days to appeal against the death sentence.
The death penalty is applied in Vietnam in cases of trafficking of 100g of heroin or more. In late 2013, Vietnam adopted the use of lethal injections for capital cases instead of firing squads.