McGlynn made his senior inter-county debut in 2006. A prominent part of the inter-county teams of the Jim McGuinness era, McGlynn won his first Ulster Senior Football Championship winners' medal with Donegal on 17 July2011, becoming the first man from the Glenfin club to achieve this. He had a terrific game on 22 July 2012 as Donegal retained the Ulster title for the first time in their history with a 2–18 to 0–13 victory over Down. His goal that day sealed the win and remains the only goal he has scored for his county as of . Indeed, McGlynn's first Championship point only came in the 2012 Ulster Senior Football Championship. This was against Cavan; he followed this with a point against Derry, that goal against Down in the provincial final and yet another point in the All-Ireland Senior Football Championship semi-final victory against Cork. He added another point against Mayo in the 2012 All-Ireland Senior Football Championship Final, bringing his 2012 championship season total to 1–4. For a player in the left-full-back position this is considered a remarkable achievement at senior level. He won an All Star but was unable to attend the Football Tour of New York. His next Championship match against Down was memorable for different reasons. Coming in the 2013 Ulster Senior Football Championship, McGlynn was concussed, as was teammate Ryan Bradley, causing manager McGuinness to voice fears that one of his players would receive a spinal injury or a neck injury if the behaviour of their opponents continued in this way. McGlynn made his 100th inter-county appearance against Armagh in the 2014 Dr McKenna Cup. He added a third Ulster SFC title later that year. His fourth Ulster SFC title came in 2018. McGrath scored a point in the final against Fermanagh. Not featuring until the final round of the 2019 National Football League, he came on as a second half substitute in the victory over Kildare. He collected his fifth and final Ulster SFC later that year, appearing as a second half substitute for Neil McGee in the final against Cavan. McGlynn announced his retirement form inter-county football on 5November 2019.
Personal life
McGlynn is married to Diane, who also plays for their club Glenfin. They have three children: Harry, Gracie and Lucas. A teacher by profession, he has taught at Stramore National School, Glendowan, Churchill, Glenswilly. He enjoys darts and cards.
Honours
;Donegal
All-Ireland Senior Football Championship: 2012
Ulster Senior Football Championship: 2011, 2012, 2014, 2018, 2019