Police arrested the suspect, a German citizen identified as Carsten L., on Wednesday in Berlin, the federal prosecutors office said.
"The accused is suspected of state treason," federal prosecutors said in a statement.
"In 2022, he shared information that he came by in the course of his work with a Russian intelligence agency.
As such, the BND would not be giving out any further details on the case until federal prosecutors had concluded their investigation, Kahl added.
The last time a German intelligence employee was arrested for treason was in 2014 - although then it was for betraying secrets to the U.S. Central Intelligence Agency.