Wandesford was the son of George Wandesford, 4th Viscount Castlecomer and Susannah Griffith, daughter of Reverend John Griffith and Susannah Cross, and great-granddaughter of Edward Worth, Bishop of Killaloe.
He succeeded to his father's viscountcy on 25 June 1751, and took his seat in the Irish House of Lords on 22 November that same year.
[1] He was elevated on 1 August 1758 when he was created Earl Wandesford in the Peerage of Ireland.
[3] He married Agnes Elizabeth Southwell, daughter of John Southwell of Enniscourt, County Limerick and Sarah Rose, daughter of Henry Rose, justice of the Court of King's Bench (Ireland), on 11 August 1750.
[4] His daughter Frances married John Butler, 17th Earl of Ormonde.