Scores of refugees staying at the hotel, which is supervised by the International Organisation for Migration, had tested positive for Covid-19, news reports said.
Authorities in Greece have locked down a refugee hotel housing 470 asylum-seekers amid reports on Tuesday that scores of residents tested positive for the new coronavirus.
The Migration Ministry said a pregnant woman from Somalia living at the hotel in Kranidi, 166 km southwest of Athens had tested positive.
News reports said on Tuesday that scores of other refugees staying at the hotel, which is supervised by the International Organisation for Migration, had also tested positive.
The International Organisation for Migration said it had "interpreters, psychologists, social workers and legal counsellors ... in constant contact with all stakeholders to support in this challenging situation."
The 28-year-old woman had been placed under "complete isolation in her room" and the entire hotel is under lockdown, the ministry said.
A hotel worker had tested positive for the virus but had not come to work for the past 12 days, the ministry said.
Some 100,000 refugees are currently stranded in Greece after other European states closed their borders in 2016.
Refugee camps in the country have been under quarantine in recent weeks with authorities trying to keep residents apart from locals.
Two camps on the mainland have registered cases.
The ministry this week extended the camp lockdown to May 10.
The virus has so far killed 116 people in Greece. Another 61 are in intensive care.