The high court outside the capital Kuala Lumpur found Bebou Akpo Bouraima guilty of trafficking, which carries the mandatory death penalty by hanging, his lawyer Karpal Singh said.
The German, who is of Togolese descent and is reportedly 40 years old, was found guilty of smuggling 1.5 kilogrammes (3.3 pounds) of methamphetamine at Kuala Lumpur International Airport in 2011.
"She (the judge) didn't believe his story... that his bag was intended for his girlfriend," Karpal told AFP, adding the defence would appeal the ruling.
Anyone with at least 50 grammes of the drug is considered a trafficker in the Muslim-majority south-east Asian country.
Two other Germans of Afghan descent were acquitted earlier this year for drug smuggling in a separate case.
They were arrested for smuggling more than 10 kilogrammes of methamphetamine into Malaysia in 2012. They remain in jail pending appeal, said Karpal, who also defended them.
On Monday, Malaysian authorities re-arrested an Australian man, who was acquitted of drug trafficking last week.
His lawyers, seeking his release, have argued detaining him pending appeal is unconstitutional. A court is to rule on the case next Tuesday.
Hundreds of people are on death row in Malaysia, many for drug-related offences, though few have been put to death in recent years.