Career
McCullough started his career with his local team, Loughgall Youth, before joining Dungannon Swifts where he played in the first team in the IFA Premiership at the age of 15. Manchester United
He moved to England to play for Manchester United in July 2010. He captained the Academy side throughout the 2011-2012 campaign, making 25 appearances.
On 25 January 2013, he joined Football League Two side Cheltenham Town on a one-month loan deal.
He made his league debut on 16 February 2013, in a 1–1 draw with Aldershot Town, coming on as a substitute for Steve Elliott. Doncaster Rovers
After spending time on trial during pre-season, McCullough signed a two-year deal with Doncaster Rovers on 25 July 2013.
He made his debut for Doncaster when he started in Rovers" 3–1 defeat to Brighton & Hove Albion in the Championship on 2 November 2013. McCullough first represented Northern Ireland at under-16 level where he became captain.
He was also captain of the under-17s.
Although named in the squad twice before, his first appearance for the under-19s was a start in the 8–1 victory away to Moldova on 15 October 2012. Although he didn"t score in that game, he was credited with two assists. On the same day he signed a contract with Doncaster Rovers, he also received a call-up to play for the under-21 squad in the Milk Cup.
McCullough is a Liverpool fan.