He began his professional career in the Premier League with Aston Villa and has earned two full international caps for the Republic of Ireland.
O'Halloran has gone on to play for Nuneaton Town, Stockport County, Salford City and FC United of Manchester during his NLS career.
[8] After appearing as an un-used substitute for four matches,[9] O'Halloran made his Wycombe Wanderers debut, making his first start, in a 2–0 loss against Hartlepool United on 25 November 2006.
[13] After failing to make a first team appearance under Martin O'Neill in the 2007–08 season,[14] he was loaned out to Championship side Southampton on 19 January 2008 until February 2008.
[18] In the warm up for what would have been his debut for Leeds against Swindon Town at the County Ground, he suffered a serious anterior cruciate ligament injury which kept him out for up to a year.
[20] After returning from the loan spell at Leeds United, O'Halloran revealed he had a conversation his then teammate Patrik Berger over injury.
[21] On 5 November 2008, O'Halloran signed for newly promoted Championship side Swansea City on an initial three-month loan deal as competition to Argentinian-born left back Federico Bessone.
The 21-year-old was signed to fill the gap left by fellow Irish defender Marcos Painter, who was out for the majority of the season through injury.
[27] However, a week later, O'Halloran suffered a stiff back during a pre-season friendly match against Northampton Town[28] and missed at the start of the season.
[29] After recovering to full fitness,[30] O'Halloran remained on the sidelines until on 29 December 2010, where he made his Coventry City debut, coming on as a substitute for Richard Woods in the 76th minute, in a 1–0 win over Queen Park Rangers.
[35] As a result, O'Halloran lost his first team place in the left-back by Chris Hussey and was on the substitute bench for remaining games towards the end of the season.
[45] O'Halloran made his Nuneaton Town debut in the opening game of the season, where he played at left back for 90 minutes in a 5–4 loss against Ebbsfleet United.
[53] Having become a regular in the first team, O'Halloran scored his first Salford City goal in the second round of FA Cup, in a 1–1 draw against Hartlepool United on 3 December 2015.
[55] In June 2017, O'Halloran rejoined Stockport Country, signing a one-year contract ahead of the start of the National League North season.