There has been a house and garden at Tregothnan for a very long time. When John de Boscawen Ros of St. Buryan Parish married the heiress Johan de Tregothnan in 1335, he moved his home from the Penzance area to Tregothnan, where his descendants are still living. The Tregothnan coat of arms is set over the front door; 'Tregothnan' translated from Cornish means 'The House at the Head of the Valley.'

The original house, in Plantagenet times, lay to the northwest of the present terrace, where a number of ilexes now grow. It was a two-storeyed building with a battlemented tower containing an arched doorway. Only the old doorway remains - at the entrance of the present kitchen garden. The original house was 'sacked' in the Civil War, and the present house dates from the time of the Protectorate, as confirmed by the date, 1652, carved in stone over the side door.

In 1811, Humphry Repton, Norfolkman and landscape designer, reported to Lord Falmouth that the floors of the house had dry rot and were giving way. His report contained plans for rebuilding the house and landscaping the grounds.

Repton died in 1818 and it was another Norfolkman, William Wilkins, who became the architect enlarging the house in the 1820s. Wilkins had a stream of architectural successes to his name including the National Gallery in Trafalgar Square, the improvements to King's College and new buildings at Downing College, Cambridge. Under his direction, the 1652 manor house was refaced, re-roofed and embodied in the new and enlarged Tregothnan family home.

The house stands today much as Wilkins intended.

Admiral The Hon. Edward Boscawen's cannons are mounted on the terrace of the house as a tribute to the great Cornish Admiral's victories over the French in the Seven Years' War (1756-1763). The cannons were cast at John Fuller's famous gun foundry at Heathfield in Sussex in the eighteenth century, and his initial 'F' can be seen on a trunnion on each gun. Admiral Boscawen is buried at the nearby church of St. Michael Penkivel which also contains his memorial, designed by Robert Adam.