The District Court in Sosnowiec, southern Poland, found Igor R. guilty of working for the FSB and of creating a direct threat to public safety by helping send a package containing explosive materials that prosecutors said could have caused a deadly blast.
His wife, Irina R., was convicted of aiding his espionage activities and sentenced to three years in prison.
Both defendants received credit for time already spent in pre-trial detention.
Igor R. has been in custody since July 2024 and Irina R. since November 2024, state news agency PAP reported, withholding the convicts' full names under Polish privacy laws.
The ruling is subject to appeal.
"The court accepted the prosecutors' arguments and found the defendants guilty of the crimes with which they were charged," Krzysztof Kuk of Poland's National Public Prosecutor's Office told reporters.
He said prosecutors would decide whether to appeal after reviewing the court's written justification.
Katarzyna Matejczyk, the defence lawyer for Irina R., said she would decide whether to appeal after consulting with her client.
The couple, both Russian nationals, were arrested in July 2024. Their trial began in January this year behind closed doors because of national security concerns.
According to prosecutors, Igor R. cooperated with the FSB between February and August 2022, collecting and passing information about Russian opposition activists living in Poland and the people and organisations assisting them.
Investigators said he transferred the encrypted information to his wife on an electronic storage device so she could deliver it to the FSB in Russia.
Prosecutors also accused Igor R. of participating in July 2024 in the shipment of a parcel containing nitroglycerin and other explosive components together with two Ukrainian nationals and another Russian citizen.
The package was intercepted at a courier company's warehouse in central Poland before it could be delivered.
According to Poland's Internal Security Agency (ABW), the parcel contained nitroglycerin, Soviet-made electronic detonators, a modified power bank designed as a triggering device, a metal thermos with a shaped-charge insert and powdered aluminum.
Experts concluded that the components constituted an improvised explosive device capable of causing extensive damage to infrastructure if detonated.
A Ukrainian woman accused of sending the parcel was convicted in a separate case by a court in Piotrków Trybunalski, central Poland, in August last year.
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Source: IAR, PAP