Authorities say the aircraft went down in the Aegean Sea while battling a forest fire on the island of Samos.
A firefighting helicopter has crashed in Greece while battling a forest fire on the island of Samos.
The Greek coastguard said the aircraft was carrying four people when it went down in the Aegean Sea on Wednesday afternoon.
Two crew members were found unconscious and were later confirmed to have died. The two others were rescued alive by authorities.
"The Romanian helicopter pilot was found unconscious by the Greek coastguard off Samos and transferred to the island's hospital," an official told AFP.
After a search and rescue operation, the body of a Greek crewmember was also found, fire officials said in a statement. Two Moldovan crew members were later found alive by the authorities.
The aircraft involved is believed to be a Soviet-era Mi-8 helicopter, leased for firefighting operations from Ukraine.
Greece's coastguard said on Wednesday that it has launched an investigation into the crash.
A total of three helicopters and five planes had been deployed to help firefighters tackle the blaze on Samos, according to the Greek Fire Service.
Following last year's deadly fires, foreign rescue workers have been deployed in Greece under an EU mechanism to boost resources.