Mulligan won a Donegal Senior Football Championship medal with his club in 2018, scoring three points in the final.
[1] He then played during Gaoth Dobhair's first ever Ulster Senior Club Football Championship-winning campaign later in 2018, a run which involved a quarter final defeat of Cargin (a game in which Mulligan scored a goal and a point),[2] a semi-final defeat of eleven-time winners Crossmaglen Rangers (a game in which Mulligan scored a point),[3] and culminated in the club defeating Scotstown (who had won the competition on four previous occasions), the last two of these games occurring at Healy Park in Omagh.
[4] Mulligan won the 2014 Ulster Minor Football Championship title with Donegal; they defeated Armagh in the final.
[7] First featuring at senior level for his county under the management of Rory Gallagher, Mulligan started against Monaghan and against Mayo during Donegal's Division One campaign in the 2017 National Football League.
[8][9] Under the management of Declan Bonner, Mulligan made a substitute appearance against Cavan in the preliminary round of the 2018 Ulster Senior Football Championship, scoring a goal as his county progressed to the quarter-final.