Siemens said in a statement it will supply signalling technology and components for a 16-kilometre extension of two subway lines in the Greek capital.
The subway extension was designed to help alleviate the traffic chaos in Athens, reducing the number of cars on the city's streets and cutting carbon emissions, Siemens said.
Construction is expected to begin next year.
The Handelsblatt business-focussed newspaper said on Wednesday that the Greeks had got a bargain, as around 70 percent of the project was being financed via EU funding – while Siemens should thus have no concerns about being paid.
A years-long row between the German company and the Greek government over bribery payments to Greek officials was settled just a few weeks ago. Siemens paid €90 million to the Greek government to help it fight corruption and a further €80 million to help it pay off debts.
Former Greek minister in further German bribery case
In a further Greek-German corruption case, former Greek Defence Minister Akis Tsochatzopoulos was arrested on Wednesday in connection with the purchase of German submarines.
He is accused of accepting bribes in the Greek purchase of four submarines worth €2.85 billion in 2000. German investigators concluded that the former MAN subsidiary Ferrostaal had paid millions of euros in bribes in connection with the deal.
Ferrostaal has already paid nearly €140 in fines while two of its former managers were jailed for two years in December 2011, and both fined.