The average price for an overnight stay in the city in August has risen 39 per cent month-on-month to £207, up from £149 in July.
It is the first time in 18 years that the Edinburgh International Festival and Edinburgh Festival Fringe are running simultaneously from 7 – 31 August.
Hotels rates in the city are on average £38 more expensive than in London this month, despite the capital expecting record numbers of summer visitors.
Denise Bartlett, of Trivago UK Public Relations, advised festival attendees to look for rooms outside the city.
She said: “For those still seeking accommodation a nearby town or city might be their best bet, with availability low and prices high in Edinburgh.
“Guests still hoping to join the festivities without a set date should consider visiting during the week, rather than the weekend. The most expensive accommodation prices in Edinburgh are found on each of the Saturday nights, with hotel prices approximately 20 per cent cheaper during the week.”
Saturday 8 August is currently the most expensive day for lodging with rooms costing an average of £237, up 44 per cent on the previous weeks' price of £164.
High costs have not spread throughout Scotland, with hotels in Glasgow costing an average of £107 a night this month – 93 per cent cheaper than Edinburgh.
In Dundee and Perth prices decreased compared to July, falling 18 per cent and eight per cent respectively.
The Scottish capital has topped a list of the most expensive UK destinations this summer, with Bath, St Peter Port, Oxford and London rounding out the top five.