Archibald was born around 1580 probably in Cochno, Dunbartonshire, Scotland, the second son of Claud Hamilton and his wife Margaret Betoun.
[1] His father's family was a cadet branch of the House of Hamilton founded by Walter fitz Gilbert of Cadzow.
While still in Scotland he married his first wife, who probably was Alison Hay, who had been a nurse to Elizabeth, Queen of Bohemia.
[4] He was nominated Bishop of Killala and Achonry on 8 March 1623[5] and consecrated 29 May that same year in St. Peter's Church, Drogheda.
[8] The temporalities of his see having been much diminished by Miler Magragh, Hamilton petitioned Thomas Wentworth for their recovery.