German daily Bild said on Saturday it had obtained a copy of a letter and contract from TUI to hoteliers, reserving the right to pay in the new currency, should Greece drop the euro.
A spokesman for the travel operator, Robin Zimmermann, confirmed the report.
"We have to protect ourselves against these kinds of currency risks," he told Bild. "There is more than a theoretical possibility that Greece will leave the eurozone."
Experts say that a new Greek currency could lose up to 60 percent of its value shortly after it is introduced.
The board chairman of the Association of Greek Tourism Enterprises (SETE), Andreas Andreadis, told the paper that a number of hotel owners in Greece had received the letter from TUI requesting them to sign a new contract.
"No hotelier is going to do that, and we have appealed to the Greek tourism ministry," he said. "TUI cannot pressure any hoteliers into signing something like this."
The notion that Athens could default on its debt has raised fears of a domino effect that could shake other debt-burdened eurozone members, such as Italy.
As the crisis continues to weigh on financial markets, speculation that Greece could leave the eurozone and revert to its former currency, the drachma, is growing.