UEFA says Panathinaikos face a one-season ban from European competition if they fail to pay creditors this month.
The Greek club had a €100,000 fine imposed by UEFA's club finance panel, with a further €100,000 due if Panathinaikos haven't "paid the amounts or concluded an agreement with the creditors" by March 1.
UEFA did not specify the debts, but the European football governing body has the power to intervene if clubs delay paying wages, transfer fees or taxes.
If Panathinaikos miss the deadline, the club will be excluded the next time they qualify for the Champions League or Europa League until 2021, missing out on millions of euros in potential revenue.
The 1971 European Cup finalists are eighth in the 16-team Greek Super League. They last played in Europe two seasons ago, losing in the qualifying rounds of both UEFA competitions.