The High Court in central Selangor state found 37-year-old Mariko Takeuchi guilty of transporting 7.7 pounds (3.5 kilograms) of methamphetamine in a suitcase when she flew from Dubai into the Kuala Lumpur International Airport on Oct. 30, 2009.
Takeuchi is the first Japanese convicted of drug trafficking in Malaysia. A conviction carries a mandatory death penalty.
Takeuchi's lawyer Mohamad Rafik Rahem said Tuesday they will appeal the verdict.
The court rejected Takeuchi's claim that she had not known about the drugs and was carrying the suitcase as a favor for an Iranian acquaintance.
Mohamad Rafik said Takeuchi was "very sad and disappointed."