The 47-year-old man — identified only as Long N.H. in keeping with German privacy rules in judicial cases — was charged with working for a foreign intelligence service and aiding in an abduction.
The charges each carry up to 10 years' prison. No trial date has been announced.
Germany believes Long N.H. took part in the brazen kidnapping, denied by Hanoi, of state company executive Trinh Xuan Thanh, who has since been sentenced to two life terms in Vietnamese high-profile corruption trials.
Thanh, who was in Germany seeking asylum, was snatched last July 23 while walking in Berlin's central Tiergarten park and reappeared days later, in police captivity, on Vietnamese state TV.
Vietnam has insisted he voluntarily turned himself in, but Germany says he was abducted in a “scandalous violation” of its sovereignty in a kidnapping that Foreign Minister Sigmar Gabriel said evoked “thriller movies about the Cold War”.
German federal prosecutors charge that the detained suspect rented a Volkswagen van in Prague and drove it to Berlin, where several armed men dragged Thanh and a female companion into the vehicle.
The prosecutors said Thanh and the woman were first taken to the Vietnamese embassy in Berlin before she was flown to Hanoi and Thanh “was abducted to Vietnam by unknown means”.
The kidnapping “was carried out by Vietnamese intelligence officials and other Vietnamese embassy staff in Berlin and several Vietnamese nationals living in Europe, including the accused,” said the prosecutors.
Long N. H. was tasked with renting the abduction van in Prague and later returning it, and with also driving back a rented BMW sedan that had been used for observation, they said.
He was arrested in the Czech Republic on August 12 and extradited to Germany on August 23.
The one-party state of Vietnam has waged an aggressive anti-corruption purge but analysts say it is often driven by infighting within the wealthy business-political elite as much as a true commitment to ending graft.
Thanh, the former head of PetroVietnam Construction Corporation, in two high-profile trials early this year received two life prison sentences for embezzlement and causing losses to the state.