A Swedish tech consultant was handed three years in jail on Wednesday for selling sensitive information about truckmaker Scania to Russia, the district court said.
Prosecutors said the 47-year-old man's actions could have compromised Sweden's national security.
It was the first espionage trial in the country in 18 years, according to broadcaster SVT.
The man was arrested in February 2019 while dining at a restaurant in central Stockholm with a Russian diplomat suspected of being an intelligence officer.
The diplomat was briefly detained but released because of his diplomatic immunity.
At the time of his arrest, the consultant had just received 27,800 kronor ($3,200, 2,700 euros) for passing information to Moscow, prosecutor Mats Ljungqvist said in February.
The court found he had copied "secret information" from Scania, which he had transferred to USB-drives and handed to a Russian embassy worker.
In a statement, it added that he had been "fully aware that the information he had delivered would benefit Russia".
The information concerned "manufacturing, such as source codes and construction of products in the automotive sector", court documents showed.
The man was also found to have delivered information from carmaker Volvo but he was cleared of spying charges because the information could not be proved to have "hurt Sweden's security".
Much of the trial was held behind closed doors because it dealt with issues including "Sweden's relation to foreign powers, defence abilities, intelligence work" and corporate secrets, the court said.
In its latest annual report published in 2020, Sweden's intelligence agency said Russia, along with China, posed the biggest intelligence threat to the Scandinavian country.