The site of Killarney House was chosen by Queen Victoria on her visit to Ireland in 1861. This house was the replacement for Kenmare House (1726) as the seat of the Earls of Kenmare.
It was Valentine Browne, 4th Earl of Kenmare, who decided to build a new mansion on a hillside with spectacular views of Lough Leane in 1872. The old manor, Kenmare House, was demolished and an Elizabethan-Revival manor house on a more elevated site erected. The cost was well over £100,000.
This house was supposed to have been instigated by Lady Kenmare (Gertrude Thynne, granddaughter of Thomas Thynne, 2nd Marquess of Bath) and inspired by Lord Bath's genuinely Elizabethan seat, Longleat, Wiltshire (which is not red-brick); but it was not unusual for the descendants of Elizabethan or Jacobean settlers in Ireland to assert their comparative antiquity in this period by building Jacobethan houses. The architect was George Devey but, according to Jeremy Williams, "... that feeling of being built up over the centuries that distinguished Devey's work was entirely lacking, partly due to the job being supervised by W.H. Lynn [the Belfast architect] at his most relentless ... The western-most gate lodge, gabled and galleried, [which survives, is] Devey at his most delightful."
The house, in addition to its other defects, apparently did not sit happily in the landscape as it had many gables and many oriels. The interior was pannelled and hung with Spanish leather. It was considered one of the finest mansions in Ireland. Sadly, it was burnt out twice - once in 1879, just after its completion, and again, and finally, in August 1913 and never re-built. Instead Valentine Browne, 5th Earl of Kenmare decided to convert the nearby stable block of the old Kenmare House for family use, also naming it "Kenmare House".
In 1956 Mrs. Beatrice Grosvenor CBE (1915-1985), niece of the seventh Gerald Ralph Desmond Browne, 7th Earl of Kenmare (1896–1952) and granddaughter of the Duke of Westminster, built Knockreer House on the site of the former "Killarney House". The house was designed by Mrs. Grosvenors cousin, Francis Pollen (1926–87). Knockreer House and the surrounding land, formerly part of the Kenmare Estate of the Earls of Kenmare, were later donated by Mrs. Grosvenor to form Killarney National Park.