The gardens were originally established alongside Threave House, built in 1872 on rising land to the east of the valley of the River Dee, near Castle Douglas and commanding excellent views west to the hills of Galloway. Threave House was built by William Gordon, a Liverpool businessman who had bought the Threave Estate as a summer home for his extensive family in 1867.
The house and estate were passed to the National Trust for Scotland by William's bachelor grandson, Major Alan Gordon, in 1948. The NTS have since continued to maintain and develop the 24 hectares of gardens around Threave House as a visitor attraction. The gardens also serve as a live classroom for the NTS's School of Practical Gardening, which offers much sought after one year courses in the practical skills of amenity gardening.