The "more than 10,000 data entries" related to Swiss bank accounts with assets totalling the equivalent of €3.7 billion ($3.9 billion) held by both individuals and companies, said the finance ministry of North Rhine-Westphalia in a statement issued on Wednesday.
"The Greek government is taking an important step to bring about more tax honesty in the country," said the state's finance minister Norbert Walter-Borjans.
"We in North Rhein-Westphalia are supporting the authorities there," he said.
"Thanks to the successful work of our tax investigators, we are able to help."
The western state, Germany's most populous, has in recent years purchased data relating to Swiss bank accounts in its bid to clamp down on tax cheats.
Greece's Finance Minister Trifon Alexiadis welcomed the information and said the authorities will seek more details from Switzerland.
The government of cash-strapped Greece has been struggling to fight against a deeply ingrained culture of tax evasion, with many people making little secret of their preference of doing business in cash to avoid paying tax.
Greece's finance ministry estimates that the country loses up to 20 billion euros a year to tax evasion and smuggling.
Germany helped broker a series of European bailouts for Greece to head off it defaulting on its debts but insisted on strict reform commitments in return, including a crackdown on tax dodging.