Maria Elvira Pinto Exposto, 54, from Sydney, was caught with methamphetamine in her bag as she caught a connecting flight to Melbourne in 2014, but she maintains she was conned into the situation by an online boyfriend.
The grandmother, and mother-of-four, told law enforcement she was on her way back from Shanghai where she met a US serviceman who she was having a romantic online romance with.
Exposto claims she was asked to carry a bag full of clothes, but was unaware it contained 1.5kg of crystal meth.
She was initially found cleared of any wrongdoing but on Thursday an appeals court overturned the verdict and sentenced her to death.
Tania Scivetti, Exposto's lawyer, said: 'It's disappointing as there was clear evidence that she was the victim of an Internet romance scam. She was a drug mule.'
Malaysia has a mandatory death sentence for anyone found guilty of carrying more than 50g of a prohibited drug.
In a statement on Thursday evening Foreign Minister Julie Bishop said 'Australia opposes the death penalty in all circumstances for all people'.
She said the Department of Foreign Affairs and Trade would continue to provide full consular assistance to Ms Exposto in Malaysia following the overturning of her acquittal and imposition of the death sentence.
This article originally appeared on New Idea.