Four pallets with 75 boxes full of fake notes were found during raids at a house in the northern town of Jübek and two business addresses in Hamburg.
The forgeries could be "identified on closer inspection", investigators in Kiel said in a statement.
But the bills could also be "mistaken for real money" in the opinion of the German central bank and US authorities.
German police received a tip-off from US investigators which led them to the stash.
The dodgy cash was suspected to have come from a "wholesaler in Turkey", storing the bills in Germany on their way to the United States.
The cash was found at an address linked to a 42-year-old, who was suspected of "already having exported counterfeit money to the United States".
The suspect, who runs two export businesses, is being investigated by prosecutors for counterfeiting money but has not been arrested yet for lack of direct evidence linking him to the crime.
"Both the production and procurement, as well as the entry into circulation of counterfeit notes constitutes an offence," police said.
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