[1] The eldest son of Isaac Milles the elder, he was born at Barley, Hertfordshire, on 19 June 1671.
[2] Having been ordained by Bishop John Hough, he became chaplain of Christ Church, Oxford, in 1694, and was from 1695 to 1707 vice-principal of St Edmund Hall.
In April 1707 he went to Ireland as chaplain to the new lord-lieutenant, Thomas Herbert, 8th Earl of Pembroke, and on 11 March 1708 was appointed bishop of Waterford and Lismore.
[2] Milles published in 1703 a folio edition of the works of St Cyril of Jerusalem, with Greek and Latin notes.
He also published:[2] An Account of the Life and Conversation of Isaac Milles of Highcleer [his father], London, 1721, is also attributed to him.