Career
Manchester City
McDermott began his career at Ashbourne United then moved to Cherry Orchard of Dublin, where he was scouted, and signed up by Manchester City. In September 2008, McDermott joined Football League One side Milton Keynes Dons on a one-month loan deal, making his début against Oldham Athletic. This would turn out to be his only appearance for the MK Dons as his loan spell was ended prematurely due to injury.
McDermott returned to Manchester City where he remained in the reserves for the remainder of the season.
At the start of the following season he signed a new two-year deal to stay at the City of Manchester Stadium. After signing the new contract, McDermott joined Football League Two side Chesterfield on a three-month loan deal.
Towards the end of the January 2010 transfer window McDermott went out on loan for a third time, this time until the end of the season at Championship side, Scunthorpe United. Foreign the first seven months of the 2010-2011 season Donal continued to play for the Manchester City Elite Development Squad before going out on loan for a fourth time on 24 March 2011, this time to Football League One club Bournemouth.
He helped the Cherries reach the Play-offs following a sixth-placed finish by scoring against Huddersfield in the first leg but they were defeated on penalties by Huddersfield on the second legal
That was his only goal on loan at AFC Bournemouth. Huddersfield Town
On 1 July 2011, he signed a two-year contract with Huddersfield Town on the expiry of his contract at Eastlands. As he was offered a new deal, the fee will be decided by a tribunal.
He made his Terriers debut in the 1–1 draw against Bury at the Galpharm Stadium on 6 August 2011.
AFC Bournemouth
On 31 January 2012, McDermott made a permanent switch from Huddersfield to return to Bournemouth. Dundalk
On 5 July 2014, McDermott made a permanent switch from Bournemouth to Dundalk.
He went on to play 12 times winning the league with Dundalk. Rochdale
On 7 May 2015, McDermott signed a one-year contract with Rochdale.
Dundalk
League of Ireland (1): 2014.