He was born at Dowth in County Meath, son of John Netterville and a daughter of Christopher Barnewall, 2nd Baron Trimlestown, and Elizabeth Plunkett.[1] The Nettervilles were an old Anglo-Irish family which had already produced one leading judge, Nicholas de Netterville, who like Thomas sat in the Common Pleas (1301-9). Luke Netterville (died 1560), another Irish judge of the era, was Thomas's younger cousin and brother-in-law (they married sisters of the St Lawrence family) and was the ancestor of Viscount Netterville.[2]
Thomas was studying law at the Inner Temple in 1507.[3] He was Chief Justice of the Liberty of Kildare in 1518.[1] He became a judge of the Court of Common Pleas (Ireland) in 1521, and probably died in office in 1528.[1]
He married Elizabeth, daughter of Nicholas St Lawrence, 4th Baron Howth and his first wife Genet Plunkett; they had no children.[4]