Knockelly is reputed to have been built by Edmund Fitz James Butler, 8th Baron Dunboyne for his second son Piers, with work commencing in c1465. The castle remained within various lines of the Butler family until 1592, when Peter Oge Butler rebelled against the crown, and Knockelly was granted to Patrick Grant, a nominee of the 10th Earl of Ormond. By 1602, Knockelly was the property of Sir John Everard (d.1624), who was most likely responsible for the c1610 renovations. Everard was admitted to the Inner Temple in London in 1578, called to the bar in 1590, but returned to Ireland and had been made Justice of the Liberty of Tipperary by 1601.

Knockelly was retained within Everard lines until Sir Redmond Everard, 4th Baronet, supported the failed Jacobite rising of 1715 and had to flee to France where he lived out his days. During Sir Redmond’s exile, funds were short and Knockelly was occupied by a series of notable tenants, including the Jolly’s, the Lowes and the O’Callaghans, until the castle and entire Everard patrimony, was acquired by Thomas Barton, a powerful wine merchant, in c.1751.

The Barton estate included Grove, an important house and lands to the south, and Knockelly may have served as an agents house for the estate. It is believed the 1830 renovations to the Gatehouse may have happened then. Knockelly was eventually let to James Kickham, one of whose daughters, Catherine, married a Patrick Heffernan. The Bartons, whose estate had been reduced from 5,000 to 500 acres, sold Knockelly between 1904-1906 to the Heffernans, who lived there until the present owners purchased the property in 2020.