In April 1980, his secondary school De La Salle College Ballyshannon, defeated Leinster champions St Mary's CBS, Portlaoise, by 2–10 to 1–6 to win the All-Ireland Colleges B title at Croke Park, with Gallagher playing in the final.[3][4]
Matt Gallagher played for Donegal from 1981 until 1995. He suffered from appendicitis in 1983, causing him to miss Donegal's victory over Cavan in the Ulster final and the All-Ireland semi-final.[7] He fell out with manager Tom Conaghan during the 1980s.[8] He missed the 1989 Ulster SFC final.[9]Brian McEniff restored him to the team in time for the 1990 Ulster SFC, and Gallagher played against Armagh in the 1990 Ulster final, won by Donegal.[8] He was a key member of the county's 1992 All-Ireland Senior Football Championship winning team.[1] A utility player often deployed as a defender, Gallagher started at full-back in the 1992 All-Ireland Senior Football Championship Final in which Donegal defeated Dublin by a scoreline of 0-18 to 0-14. Later that year he won an All Star for his performances in that campaign.[5]
He played his club football for Aodh Ruadh and Naomh Bríd.[1]
After retiring from inter-county football in 1997, he joined then-manager Declan Bonner's backroom team.[5][10] He briefly served under McEniff in 2003 [11] and has also managed Naomh Bríd.[12]
^ abc"Gallagher, Matt". Hogan Stand. 17 July 1992. Above everyone else though, the player shortlisted by most commentators as their Player of the Provincial Championships is Donegal's Matt Gallagher. Now in his eleventh championship season with his native Donegal, the rock-solid stopper has been nothing shorts of brilliant over the course of his county's three match gallop to the Ulster senior Championship final showdown, which takes place on Sunday next.
^"Roper heads into the sunset". Donegal Democrat. 12 January 2010. Archived from the original on 18 February 2013. Retrieved 12 January 2010. If ever a man deserved trumpeting and a fanfare Brian Roper deserved one. After he all is Donegal's most capped player. He beat Matt Gallagher's long standing record last year and when he finally shook hands with John Joe Doherty, he had played 159 games between league, championship and Dr. McKenna Cup.
^McHugh, Michael (23 April 2020). "De La Salle's 'Band of Brothers' recalled on 40th anniversary of All Ireland Colleges victory: The Donegal school of 155 students that made history in 1980 for Ballyshannon". Retrieved 23 April 2020. A tilt at the All Ireland series was complicated by the fact that the age limit was actually younger than the Ulster competition and lads including the late Pauric Gallagher… had to be dropped for the semi-final against a Paul Early marshalled Ballyhaunis at a wet and windy Markievicz Park in Sligo… The DLS team and subs included: Thomas Cleary; Pauric McLoone, Paschal McTernan, Conor Boyle; Thomas Gallagher, Tommy McDermott, Paul Tuohy; Brian Tuohy (Capt.), Matt Gallagher; Martin Williamson, Michael McHugh, Tom McMahon; John Lee, Brian Murray, Pauric Bromley. Subs: PJ Ward for John Lee; Eunan Gallagher, Eunan Doyle, Conor Maguire, Tommy McLoughlin, Declan Gallagher… Indeed, a number of that winning All Ireland team and younger Loch an Iuir success went on to distinguish themselves in the green and gold of Donegal and Ulster. These included Gary Walsh, Matt Gallagher and Brian Murray, who all played vital roles in Donegal's first ever All Ireland senior football final victory against Dublin in 1992.
^Campbell, Peter (15 July 2008). "Donegal heroes of 1983". Donegal Democrat. Archived from the original on 18 December 2015. Retrieved 15 July 2008. The game was to be the only game for young corner back, Matt Gallagher, who picked a hand injury before the semi-final and appendicitis ruled him out of the Ulster final and All-Ireland semi-final.
^Campbell, Peter (28 September 2017). "Why can't Donegal unite behind new manager Declan Bonner?". Retrieved 28 September 2017. It's not as if Declan Bonner hasn't served his time. He was just 32 years of age the last time he took on the mantle. It's hard to imagine that a 32-year-old would be given the job nowadays. Back then his assistants, Matt Gallagher and Charlie Mulgrew, weren't much older.
^"Breaking Ball: Donegal Club Championships 2019". Donegal News. 6 September 2019. p. 48.
^McNulty, Chris (4 December 2012). "Ulster GAA Writers to hold landmark bash in Donegal". Donegal News. Retrieved 4 December 2012. Current All-Stars Karl Lacey, the 2012 Footballer of the Year, and Michael Murphy have been short-listed, as have 1992 All-Ireland winners Martin McHugh, Anthony Molloy, Matt Gallagher and Tony Boyle.
^McNulty, Chris (12 December 2012). "Donegal take the top writers' awards". Donegal News. Retrieved 12 December 2012. Lacey, meanwhile, was named on the UGAAWA Jubilee Team, a selection which caused widespread debate, with some surprise in Donegal that neither of Martin McHugh or Tony Boyle were named.