O'Halloran, was born in Ireland, (or born at Berhampore, India, and came to England in 1811) the son of Major-General Sir Joseph O'Halloran, G.C.B., a grandson of Irish surgeon Sylvester O'Halloran, and brother of Thomas Shuldham O'Halloran.
He entered the army as ensign in the 14th Foot in 1823 (or 11 January 1824), and after brilliant service in India, particularly at the siege and storming of Bhurtpore, Bengal (medal), obtaining his lieutenancy in action. In the latter year he embarked for Sydney with a detachment of the 50th regiment. Thence he sailed for Calcutta, joined the 38th regiment at Chinsorah in 1835, and accompanied it to England in 1836.
He obtained his company by purchase on 29 Dec. 1837, and retired from the army in April 1840. O'Halloran emigrated to South Australia in 1840.
He was appointed Auditor-General, in succession to Francis Singleton, in 1851, and held the position till 1868, when he finally retired from the public service. He died on July 15, 1885. Captain O'Halloran married in 1831 Eliza Minton, daughter of John Montague Smyth.
In that colony in August 1841 he was appointed a justice of the peace, appointed a member of the Audit Board in 1843, and subsequently became private secretary to Governor Sir George Grey, and clerk of the Executive Council.
