As Lord Conway's secretary or agent, he generally lived in his house near St. Martin's-in-the-Fields, but paid frequent visits to his employer's country seats and to his Irish property. When in Ireland he lived in one of Conway's houses at Brookhill, five miles north-west of Lisburn, commanded a company of soldiers there in 1635, and sat in the Irish parliament of 1639 as member for Belfast.
When the Irish rebellion broke out on 23 Oct. 1641, Rawdon was in London. He posted down to Scotland, crossed to Bangor, and reached Lisburn on 27 Nov. He found the town held by Sir Arthur Tyringham, with Lord Conway's troop and some badly armed raw levies. Sir Phelim O'Neill came next morning, but was twice beaten off with great loss. In their retreat the Irish burned Brookhill with Conway's library in it and much property belonging to Rawdon, who was wounded and had a horse shot under him (Ulster Journal, i. 242; Warr of Ireland, p. 13). Rawdon was one of those to whom Sir Phelim some weeks later wrote letters with the signature ‘Tyrone,’ after his mock investiture at Tullaghoge (Hickson, i. 227). Conway's troop of horse was expanded into a regiment, the officers being appointed by the English parliament, and Rawdon became major.
In June 1642 Rawdon served under Monck in the neighbourhood of Armagh, and again had a horse shot under him in a skirmish with Sir Phelim O'Neill (Benn, p. 686). Rawdon employed his men in reaping the Irish harvest of 1643, and endeavoured to maintain the September armistice. He was in Belfast when it was surprised by Monro in May 1644. In the following July he took part in the indecisive affair with Castlehaven near Dromore (Warr of Ireland, p. 40). In 1645 he was major of Colonel Hill's regiment of horse, and continued to serve in Ulster till 1649, being often in command of the cavalry. He retired from military service soon after the death of Charles I. Monck, who was his intimate friend, thought he would have been wiser ‘to continue in command and keep all right’ (Rawdon Papers, p. 77). He was a commissioner of revenue for the Belfast district during the Commonwealth, but refused to serve under Monck in Scotland. After the Protector's death he was active in preparing for the Restoration, and in June 1659 he made a journey to Scotland to consult Monck. He was made one of the commissioners for executing Charles II's declaration of 30 Nov. 1660 as incorporated in the Act of Settlement (Irish Statutes, 14 & 15 Car. II, cap. ii.), sat as member for Carlingford in the Irish parliament of 1661, and was made a privy councillor. In May 1665 he was created a baronet, and in the following year received large grants of land, especially the forfeited estate of the O'Laverys in Down, and other property in Dublin, Louth, and Meath. These rewards were for service done before June 1649. He built the town of Moira in co. Down, which was created a manor and filled it with ‘conformable protestants.’ About this time Rawdon was active in obtaining the help of Valentine Greatrakes [q. v.] for his invalid sister-in-law, Lady Conway (Rawdon Papers, p. 212). In the following year he was employed in organising the Ulster militia (ib. p. 217), and this engaged his attention as late as 1681 (ib. p. 273). He was generally occupied in improving his own property as well as Lord Conway's, and is called the ‘best highwayman in Ireland,’ all the roads in his district being very good (Dobbs). He was intimate with Jeremy Taylor both before and after his elevation to the bishopric of Down, and was always hostile to the presbyterians. Rawdon was generally consulted by Ormonde and others in all matters affecting the peace of Ulster. He died in August 1684, and was buried with much pomp at Lisburn.
Rawdon married, in 1635, Ursula, daughter of Sir Francis Stafford, and widow of Francis Hill, but she and her only child died in the following year. On 4 Sept. 1654 he married at Arrow church, Warwickshire, Dorothy, eldest daughter of the second Lord Conway, by whom he had seven sons and three daughters. His portrait was engraved by R. White (Bromley). His third but eldest surviving son, Arthur (d. 1695), was grandfather of John Rawdon, fourth baronet and first earl of Moira (1720–1793). He was educated at Dublin University, was elected F.R.S., and in 1750 created Baron Rawdon of Moira in the peerage of Ireland. In 1761 he was advanced to the earldom of Moira, and died on 20 Jan. 1793, being succeeded by his eldest son [see Hastings, Francis Rawdon-, first Marquis of Hastings and second Earl of Moira].
[Foster's Pedigrees of Yorkshire Families; Berwick's Rawdon Papers; Cal. State Papers, Dom. 1631–7, and 1670–1, which contain many letters from Rawdon; Ulster Journal of Archæology, vol. i.; Hist. of the Warr of Ireland by a British officer in Sir John Clotworthy's regiment; Strafford Letters; Gilbert's Contemp. Hist. of Affairs in Ireland; Ireland in the Seventeenth Century, ed. Hickson; Hill's Montgomery MSS.; Reid's Presbyterian Church, ed. Killen, vol. ii.; Dobbs's Brief Description of Antrim, in Hill's Macdonnells of Antrim, App. ii.; Heber's Life