Kilgraston’s earliest records date back to the 13th century when it was called Gilgryston.

John Grant, the eldest son of Patrick Grant of Glenlochy purchased the house towards the end of the 18th century from the Murray and Craigie families. He had made his wealth in Jamaica, where he was a member of the Assembly there and eventually succeeded Thomas French as Chief Justice of that island in January 1783, a post he held until 1790.

The mansion was used as a private home until World War I during which it was used as a hospital. In 1930 the house and grounds were purchased by the Society of the Sacred Heart and opened as a school with 40 boarders. The Society ran the school as a charitable trust until 2000 when it became an independent school. It briefly participated in the Assisted Places Scheme during the 1990s until its abolishment. In 2003, it absorbed the nearby all-girls Butterstone Prep School due to the latter’s financial difficulties. Its girls were transferred 22 miles to Kilgraston in a controversial and highly unpopular move. One of the boarding houses was named Butterstone after the school.

In January 2012, Kilgraston was named “Independent School of the Year” ahead of 27 other independent schools across Britain at the Independent School Awards.