Born in Belfast, McCann played in the Distillery youth system from 1995 until signing for the West Ham United Academy of Football in 1996, where he started his professional career.

[5] Despite only making a handful of substitute appearances for West Ham and never starting a game, he is remembered for scoring an unfortunate and bizarre own-goal during an infamous 1–7 away defeat to Blackburn Rovers on 14 October 2001.

After coming off the bench, McCann attempted a clearance from inside his own penalty area but the ball somehow spun backwards behind him and past Shaka Hislop in the West Ham goal.

[13] On 24 May 2010, Peterborough United announced that they had beaten off competition from a host of Championship clubs to secure the services of McCann on a three-year contract.

[16] On 14 January 2015, McCann returned to his native country to join NIFL Premiership side Linfield on a free transfer after his contract at Peterborough was terminated by mutual consent.

[17] McCann, who made close to 200 appearances in all competitions for Posh, had been assisting with the coaching of Peterborough's youth side in the weeks prior to his departure, but was keen to continue playing regularly.

[18] His brother, Ryan McCann, had previously played for Linfield between 2002 and 2005, winning several trophies with the Blues including the league title in 2004 and the Setanta Cup in 2005.

On 23 February 2015, McCann was linked to a coaching role at his former club Peterborough United, following the sacking of Darren Ferguson two days earlier.

On 26 February 2015, Linfield confirmed that McCann's contract had been terminated with immediate effect, facilitating his return to Peterborough in a coaching capacity until at least the end of the 2014–15 season.

[26] McCann was appointed as head coach of Championship club Hull City on 21 June 2019 on a one-year rolling contract.

[30] McCann immediately led the team back to the Championship as League One Champions, winning promotion with two matches left to play after a 2–1 victory at Lincoln City.

[31] The title was secured the following match with a 3–1 victory over Wigan Athletic, as second-placed Peterborough United were held to a 3–3 draw, a result that still saw them promoted.