The early 18th-century house is an A listed building, and was designed by Sir William Bruce.

[2] Mertoun was a property of the Halliburton family, who sold it to Sir William Scott of Harden in around 1680.

[5] Around 1750 improvements were made to the house when Walter Scott of Mertoun married Lady Diana Hume Campbell, a daughter of the Earl of Marchmont.

[2] The Scotts sold Mertoun in 1912 to John Egerton, Viscount Brackley (later 4th Earl of Ellesmere), who carried out alterations to the house and gardens.

The house was reduced to its original size in 1956, by the architect Ian Gordon Lindsay, removing the 19th- and 20th-century additions.