Home rental website Wimdu.co.uk has claimed a 45% increase in inquiries for stately homes this month, with many reportedly citing an influence from the ITV1 period drama.
Carr Hall Castle in Yorkshire is said to be especially popular with American tourists wanting to emulate Downton Abbey.
Owner Terry George said: "The popularity of shows such as Downton Abbey have certainly inspired our guests to come and stay with us.
"Americans in particular love the idea of living like a lord for a weekend. We've even been asked if the castle comes with a butler service, which we were happy to provide!"
Wimdu founder and CEO Arne Bleckwenn added: "This castle really gives you the chance to live like a Lord or Lady."
Meanwhile, Premier Inn has claimed that the third season of the show has inspired an 82% increase in visitors to its Newbury/Thatcham site as holidaymakers visit sites, like Highclere Castle, which feature in the show.
The Premier Inn Oxford has allegedly seen a 66% increase in bookings as it is near the real-life location of the Downton Hospital, village pub and local church.
Spokeswoman Claire Haigh said: "Downton fever has certainly taken over the nation's living rooms.
"It is great that such shows showcase what the country has to offer - these sites are some of the UK's national treasures and it is wonderful that this truly British drama has encouraged people to visit them."