Underage McBrearty used to play association football with
St Catherine's — also the hometown club of Everton's
Séamus Coleman — and is a close friend of Irish association footballer
Carl McHugh, with whom he played for Ireland and went on trial at
Celtic. At Celtic he trained alongside the likes of
Bobo Baldé and
Thomas Gravesen. He has also played soccer for
Finn Harps at underage level. He also played underage for his local club Kilcar and has won many titles alongside his brother
Stephen. He also played in the teams that lost to
Cavan in the 2013 and 2014
Ulster Under-21 Football Championship finals.
Inter-county 2011 season McBrearty was drafted into the senior panel by manager
Jim McGuinness in May 2011 ahead of Donegal's opening
Ulster Senior Football Championship game against
Antrim. He made his senior debut against Antrim as a substitute. He had earlier played for Donegal in the
Minor Championship, also against Antrim. He made his first senior start for Donegal against
Cavan at 17 years of age and scored 1–3. His 20th-minute goal was fired first time along the ground into the Cavan net after a pass from
Mark McHugh. McGuinness named McBrearty as a late replacement for his clubmate
Michael Hegarty in the starting lineup in that game against Cavan. McBrearty's performances during his debut season at senior inter-county level drew widespread praise, both from local and national media.
2012 season By the age of 18 he had firmly established himself as a member of the Donegal senior team. After his second Ulster SFC medal in 2012,
Jim and
Rory reckoned he had trained only about 25 times with the senior team. In the All-Ireland SFC quarter-final defeat of
Kerry at
Croke Park on 5 August 2012,
Anthony Thompson knocked McBrearty out of the game with his head, causing him
concussion. McBrearty played in the
2012 All-Ireland Senior Football Championship final against
Mayo, making a notable contribution in the build-up to Donegal's second goal of the game. His attempt at scoring a point came crashing off the Mayo post after eleven minutes of the match and Mayo's Kevin Keane fumbled, dropping the ball into the path of
Colm McFadden who promptly slotted it into the back of the net.
Dublin biting incident Against
Dublin in the final game of the
2013 National Football League McBrearty sustained a laceration to the shoulder, reported to have been caused by a bite from a Dublin player. The Donegal management team took photographs of the wound, photographs of a wound which appeared to suggest had been caused by the teeth marks of a Dublin opponent. McBrearty was hospitalised after the game to have the wound examined. Accompanied by his parents, he underwent blood tests and was put on a course of antibiotics by concerned medics. The incident overshadowed the entire game and rocked Dublin's football team, according to media there. Commentators described it as "shameful". However, Dublin County Board chairman Andy Kettle reacted with indifference, rejecting the need for an investigation and complaining instead of "a hard pitch". The GAA launched a probe into the behaviour of the Dublin players. On 17 April 2013, the Central Competitions Controls Committee (CCCC) cited
Kevin O'Brien, the
2012 All-Ireland Under-21 Football Championship-winning captain, for the biting of McBrearty. However, most sources did not immediately name the player. The offence fell under Category III and a three-match ban was proposed, enough to end the player's year if Dublin were to exit the Championship at an early stage.
2013 season Stalked by "bitegate" (see above) since the end of the National League, McBrearty put in a man of the match performance against Tyrone in Donegal's opening game of the Ulster SFC. He played a crucial role in both of Donegal's goals.
Colm Cooper collected his award for him from
The Sunday Game. His quieter performance in the following game, an Ulster SFC semi-final against Down, was put down to toothache.
2014 season McBrearty received a personal message from US actress
Sarah Jessica Parker ahead of the
2014 All-Ireland Senior Football Championship final: "My body is in NYC but my heart is in Donegal. Let's take the All Ireland and Paddy, bring it home to Kilcar. From Sarah Jessica and her son James."
2015 season Under the management of
Rory Gallagher, McBrearty started the opening fixture of the
2015 National Football League against Derry and scored 0–5 (two of which were frees) in what was his 46th appearance at the age of 21. He scored 0–4 (including one free) against Dublin in the next game, at Croke Park. He started the third fixture against Cork in
Ballyshannon and contributed 0–3 (including one free) to the team's one-point victory. He started the fourth fixture against Monaghan and scored a point from a free. He started the fifth fixture against Kerry at
Austin Stack Park and contributed 0–4. He started the sixth fixture against Tyrone and scored 0–1 (from a free). He started the seventh fixture against Mayo and scored 1–3 (including one free). Donegal qualified for the NFL semi-final. McBrearty started and scored 0–4. McBrearty started the
2015 Ulster Senior Football Championship final, scoring 0–6 (four of which were frees). He had previously started the preliminary round against Tyrone (scoring 0–2), the quarter-final against Armagh (scoring 1–1) and the semi-final against Derry (scoring 0–2, one of which was a free). McBrearty scored 1–1 in the
2015 All-Ireland Senior Football Championship qualifier defeat of Galway at Croke Park and started the next game against Mayo at the same venue.
2016 season McBrearty started the opening fixture of the
2016 National Football League away to Down and scored 1–3 (two of which were frees). He started the second fixture against Cork, a ten-point win in Ballyshannon, contributing 0–4 (including two frees) to the team's victory. He started the third fixture against Mayo and scored 0–4 (three of which were frees). He started the fourth fixture, away to Kerry at
Austin Stack Park, and scored 0–3 (all of which were frees). He started the fifth fixture against Roscommon and scored 0–6 (all frees). He started the sixth fixture away to Dublin at Croke Park and scored 0–3 (including one free). He started the seventh fixture away to Monaghan in
Castleblayney and scored 0–2 (including one free). Donegal qualified for the NFL semi-final. McBrearty also started this game, scoring 0–8 (five of which were frees). McBrearty started the
2016 Ulster Senior Football Championship final, scoring 0–3 (two of which were frees). He had previously started the quarter-final against Fermanagh (scoring 0–3, including one free), the semi-final against Monaghan (scoring 0–5 (three of which were frees) and the semi-final replay against the same opposition (scoring 0–4). McBrearty scored eleven points in Donegal's 2016 All-Ireland Senior Football Championship victory over Cork at Croke Park. McBrearty's eleven-point tally went down as the highest total of individual scores recorded by a Donegal player in the same game;
Michael McLoone (1966) and
Seamus Bonner (1974) jointly hold the record for highest
score in the same match.
The Irish Times described McBrearty's display as "stunning" and noted that he had helped Donegal become the first Ulster team to reach six consecutive All-Ireland quarter-finals, a record previously only reached by Kerry, Dublin and Cork. He scored 0–3 (two of which were frees) in that quarter-final.
2017 season McBrearty started the opening fixture of the
2017 National Football League against Kerry and scored 0–4 (three of which were frees). He started the second fixture away to Roscommon, contributing 0–2 (one of which was a free) to the team's victory. He made a second-half substitute appearance against Monaghan in the sixth fixture and scored 0–2. He made another substitute appearance in the seventh fixture against Mayo. McBrearty made a second-half substitute appearance in the
2017 Ulster Senior Football Championship quarter-final victory against Antrim and scored 1–2 (both points were frees). He started the semi-final loss to Tyrone and scored 0–6 (including four frees). He started the
2017 All-Ireland Senior Football Championship qualifier defeat of Meath at
Páirc Tailteann and scored 0-7 (three of which were frees). He then started the qualifier loss to Galway at
Markievicz Park and scored 0–6 (two of which were frees). McBrearty
captained his club to the
2017 Donegal Senior Football Championship, scoring three points in the final. It was the first time his club had won the title in 24 years, having been defeated by
Glenswilly at the same stage
the previous year.
2018 season Under the management of
Declan Bonner, McBrearty started the opening fixture of the
2018 National Football League against
Kerry in
Killarney, scoring 0–10 (eight of which were frees). He scored 0–9 (including six frees) in the next game against
Galway. He scored 0–7 (four of which were frees) against
Dublin. He scored 0–4 (including one free) against
Kildare. He missed the matches against
Tyrone and
Monaghan. He then started against
Mayo and scored 0–4 (two of which were frees). In the
2018 Ulster Senior Football Championship, McBrearty scored eight points (six from play) as Donegal overcame Derry in their quarter-final encounter. He then scored six points in the semi-final victory over Down. In the final against Fermanagh, McBrearty was substituted in the 38th minute; it later emerged that he had suffered a cruciate ligament injury in the first half and this injury caused him to miss the rest of the season. He still managed to score a point for his team in the final match.
2019 season McBrearty did not play a minute of the
2019 National Football League. This included missing Donegal's victory over
Meath in the Division 2 final. In the
2019 Ulster Senior Football Championship, McBrearty scored five points (two from play) as Donegal overcame
Fermanagh in their quarter-final encounter. He scored three points (two from play) in the semi-final victory over Tyrone. In the final against Cavan, McBrearty scored five points (four from play) as Donegal claimed that season's provincial championship. McBrearty made his 100th appearance for Donegal against
Meath in the
2019 All-Ireland Senior Football Championship quarter-final. He scored 1–6.
2020 season Post-COVID disruption, play resumed
behind closed doors on 18 October, McBrearty sustained an injury during a challenge match against Roscommon which left him unable to play in the remaining league games against Tyrone and Kerry in October 2020. Sub versus Armagh in Ulster SFC semi and scored a point.
2023–2025: Donegal captaincy and retirement In January 2023, McBrearty was appointed captain of the Donegal senior team ahead of the
2023 season. He retired from inter-county football in December 2025. His former manager Declan Bonner described him as "a man who helped set high standards in training".
International rules McBrearty was called up for
Ireland ahead of the
2013 &
2015 International Rules Series against
Australia. He started the first Test at
Breffni Park, then came on in the second Test at Croke Park to smash home the goal of that game, as Ireland romped to a record-breaking victory. ==Personal life==