The present building is a neo-classical mansion built by Sir Charles Coote, 9th Baronet (1794–1864) in the 1820s to designs by the leading Irish architects, Richard (1767–1849) and William Vitruvius Morrison (1794–1838).

For much of the twentieth century, it served as a school, having been sold in 1928 by Sir Ralph Coote to the Patrician Brothers, a Roman Catholic teaching order.

In the medieval period Ballyfin was part of the cantred of Laoighis Reta, the territory of the Ó Mordha, or O'More, clan who lost out in the Laois-Offaly plantations, the most comprehensive settlement of the Tudor conquest of Ireland.

By 1637, Ballyfin was raised to manorial status, but Crosby was on the wrong side in the turmoil of the 1640s and by May 1666, the estate was conferred on Periam Pole, a recent arrival from Devon.

Preoccupied with his political career in England, Wellesly-Pole left Ballyfin uninhabited for long periods, though he continued his predecessors' improvements to the demesne, employing the landscape designer John Webb.

An ambitious, indeed ruthless, soldier, Coote (1581–1661) had carved out vast estates in Ireland and been made a baronet by James I, before being killed at the siege of Trim in the 1641 Rebellion.

Originally, Dominck Madden (died 1837) was retained and work commenced on a house built to a long symmetrical H-plan, a short distance from the present structure.

The Entrance Hall, enlivened with a richly-patterned Roman mosaic brought back from Italy in 1822, leads into the Grand Saloon in the centre of the house.

Notable features of the interior include the richness of the stuccowork and the variety of scagliola deployed while the decoration is enhanced by the exotic marquetry of the floors.

The inlaid floor of the Rotonda is based on the Lion Court of the Alhambra Palace, Granada, while the ceiling of the Stair Hall is influenced by Coleshill, Berkshire, attributed to Inigo Jones, and included in Isaac Ware's A Complete Body of Architecture (1756).

The most notable architectural addition to Ballyfin after the time of the Morrisons was a glass Conservatory by Richard Turner (1798–1881) added at some point after 1855 and accessed through a concealed door in a bookcase in the Library.