The farm has belonged to the same family since 1771, when John Morris of Clasemont, pioneer industrialist, copper master, founder of Morriston and the Mumbles Railway, bought a very large area of undeveloped country to the west of the town of Swansea, including Killlay Fawr, from Francis Greville, 1st Earl of Warwick.
There is little doubt that John, who was made a baronet in 1806 for recruiting local men to fight in the war with France, acquired the land with a view to exploiting its underlying coal seams, especially in the Sketty and Clyne districts, but there is no evidence of any mine working or smelting on the farm itself, other than some old bell pits in a wood in the north east corner on the other side of Gower Road.
Much of this land has since become the residential areas of Sketty, Killay and Dunvant but Killay Fawr remains a working farm with its fields currently providing hay and sileage. Its boundary on Hen Parc Lane and Gower Road was developed during the course of the last century as suburban housing.
The house itself was most probably rebuilt towards the end of the 19th century following a recommendation in a survey of the estate carried out in 1874. The long barn on the Western side of the farmyard is older, possibly 18th century or even earlier.
The last tenant farmer died at the age of 87 in 1990 as a result of a fire in the building. After minor repairs it briefly accommodated a homeless family. Following their departure it was left empty for ten years and became derelict.
The estate decided in 2001 to completely rebuild the interior of the house and redesign the garden, retaining only the original exterior stone walls and the chicken hut.
It has been let exclusively to holidaymakers since the completion of the renovation works in June 2002.