The Chiba District Court said it found Donna Nelson, 58, from Perth, guilty of violating the stimulants control and customs laws.
It ordered her to pay a fine of one million yen ($A10,000) as well as serving a prison term.
The Chiba court found Donna Nelson guilty of violating the stimulants control and customs laws. (AP PHOTO)
The man, whom she met online in 2020, told her he was the Nigerian owner of a fashion business.
Nelson was arrested at Japan's Narita International Airport, near Tokyo, on January 3, 2023, after customs officials found about 2kg of methamphetamine hidden under a false bottom in a suitcase she was carrying as checked luggage.
Nelson told the court she did not know that drugs were hidden in the suitcase and that she was carrying them for a man she hoped to marry.
The man, whom she met online in 2020, told her he was the Nigerian owner of a fashion business.
In 2023, he paid to travel to Japan via Laos, and asked her to collect dress samples from an acquaintance in Laos, the court said in the ruling.
She was supposed to meet him in Japan but he never showed up, according to prosecutors.
Nelson has already been in custody for nearly two years.
Donna Nelson "is the victim of a crime and not a criminal", daughter Kristal Hilaire said. (AP PHOTO)
The court said 430 days of that would be counted towards her sentence.
Presiding Judge Masakazu Kamakura said although Nelson was deceived, she had a sense that something was wrong with the arrangement and something illegal could be hidden in the suitcase, and she could have stopped.
Kamakura said Nelson was taken advantage of her desire to marry the man and there was room for "sympathy" for what she did.
He imposed a shorter sentence than would be typical for the amount of drugs she was carrying, after prosecutors had demanded 10 years in prison and a fine of three million yen.
Nelson's lawyer, Rie Nishida, said Wednesday's ruling was unjust and she planned to appeal, vowing: "We will fight until the end."
Nelson sobbed as the verdict was read out.
Members of Donna Nelson's family attended the trial and saw her for the first time since her arrest. (AP PHOTO)
One of her daughters, Kristal Hilaire, wiped away tears as she looked on from her seat in the audience.
"We are disappointed and devastated by the court's verdict in our mum's case," Hilaire told reporters outside the court.
"We maintain that our mum was the victim of a romance scam. She is the victim of a crime and not a criminal. She has always been against drugs."
Hilaire said the past few weeks had been a difficult time for the family but that they had come together to support each other and Nelson during the trial, and they would keep fighting "until we can bring her home".
But Hillaire said she was worried about how her mother, devastated and much thinner, "would handle another six years".
Several other family members who attended earlier sessions, seeing Nelson for the first time since her arrest nearly two years ago, returned home ahead of the verdict.