The historic Castle Grant went on the market on Thursday 17 April and is now under offer.
A spokesman for selling agents Strutt and Parker said: “The buyers were the first people to see the house and placed an offer within a few hours of viewing.
“This offer has now been accepted. The buyers do not wish to make any statement nor release their names.”
It went on the market with a price of £1.1 million and the firm said they would be “very surprised” if it sold below that.
Kevin Maley of Strutt and Parker said; “this has been a very quick sale for a property of this size but it is a fantastic place in a great setting at a very good price indeed”
The stately pile at Grantown-on-Spey includes mature parkland gardens, a landscaped loch and about 35 acres of private land.
Craig Whyte was evicted from the castle earlier this month after being unable to pay the mortgage.
Whyte and his former wife Kim purchased the property for £720,000 in 2006 with a 110 per cent mortgage of £800,000.
But she moved out after their marriage fell apart, and he reportedly refused to pay the £7,000-a-month mortgage for two years.
The Bank of Scotland raised a legal action against him last year after he had failed to make the repayments from 2012.
The battle came to an end at Inverness Sheriff Court when Whyte finally agreed to repossession.
He sought help from his father Tom who supervised workmen as they cleared the castle of his belongings.
The clear-out included reportedly the siphoning off of oil from the central heating system and ripping chandeliers from the ceiling to be transported back to his London home.
Castle Grant is the ancient ancestral seat of the Chiefs of the Grant Clan.
The castle has had a number of additions added over the years, with the largest expansion taking place in the 1750s.
There was an extensive programme of refurbishment undertaken and largely complete in the early 1990s and the castle was sold to Whyte with “considerable development opportunities”.
The work that had so far been undertaken is mainly on the ground and first floors and they include a cinema room, ballroom, 4 bedrooms, billiard room, library and kitchen.
Most of the bedrooms have en-suite facilities and part of the second floor incorporates a two-bedroomed self-contained guest wing.