D'Alton was born at his father's ancestral mansion, Bessville, County Westmeath, on 20 June 1792; his mother was Elizabeth Leyne.
[1] D'Alton mainly confined himself to chamber practice, and attended the Connaught circuit, having married a lady of that province, Miss Phillips.
He received many fees in the important Irish family causes of Malone v. O'Connor, Leamy v. Smith, Jago v. Hungerford, and others.
With the exception of an appointment as commissioner of the Loan Fund Board, he held no official position, but a civil list pension of £50, granted while Lord John Russell was prime minister, was some recognition.
In 1831 he also gained the prize offered by the Royal Irish Academy for an account of the reign of Henry II of England in Ireland.
At the end of his life, in 1864, D'Alton was asked to write a History of Dundalk that was completed by James Roderick O'Flanagan.