Born in
Dublin,
County Dublin, Fagan began his career as a youth player with St. Anthony's Boys and
Home Farm in his native Dublin before signing schoolboy forms with
Manchester United in 2005 at the age of 15. He was a regular for the club's youth team, scoring 16 goals in 52 appearances over his first two seasons in England, including helping the team reach the final of the 2006–07 FA Youth Cup, in which he scored in the semi-final second leg against
Arsenal as United overturned a 1–0 deficit from the first leg, before scoring in the penalty shoot-out in the final, only for United to lose 4–3. He made two substitute appearances for the reserves in 2005–06, scoring on his second outing against
Middlesbrough after coming on for
John O'Shea. He made a further nine reserve appearances in 2006–07, including his first start in a 2–0
Manchester Senior Cup win over
Oldham Athletic, followed by his first reserve team goal in a 1–0 league win over
Everton three days later; however, he struggled to break into the reserves on a regular basis in 2007–08, scoring three goals in just seven appearances, and he was released at the end of the season. After his release, Fagan began training at the
Glenn Hoddle Academy in Spain, leading to a trial period with
Huddersfield Town in March 2009, in which he scored a hat-trick on his debut for the club's reserves, before
Hamilton Academical signed him at the end of that month. After failing to secure a permanent contract with Hamilton, Fagan signed for Lincoln City in June 2009. He made his Lincoln debut on 8 August 2009 in a
League Two match against
Barnet at
Sincil Bank, which Lincoln won 1–0. He scored his first goal for the club on 18 August in the League Two match against
Bradford City at
Valley Parade, which Lincoln won 2–0. He scored four times in 17 appearances for Lincoln, but was deemed surplus to requirements at the club after the appointment of
Chris Sutton as manager in September 2009, and on 1 February 2010, he moved on loan to Spanish third-tier side
Jerez Industrial, with which the Glenn Hoddle Academy had strong links, for the remainder of the 2009–10 season. He scored two goals on his debut for Industrial, helping them come back from 2–0 down to beat Sangonera 3–2 at home. He returned to Lincoln City in May 2010, but was placed on the transfer list by Sutton, and on 31 August 2010, Fagan was released by Lincoln City. In October 2010, Fagan went on trial with
Conference National side
Gateshead, scoring for the reserves on 26 October in a 5–1 defeat against
Middlesbrough Reserves.
Bohemians In February 2011,
Pat Fenlon brought Fagan to
Bohemians just in time for the new season. Fagan signed following an earlier, unsuccessful, trial with
Shamrock Rovers where he had played in two pre-season friendlies. He scored his first goal for the club on his League debut for Bohs against
Bray Wanderers on 4 March 2011 from the penalty spot in the
Carlisle Grounds. Despite an injury hit campaign, he managed to score 11 league goals in 23 appearances and also netted for Bohs in their
UEFA Europa League tie against
Olimpija Ljubljana.
St Patrick's Athletic 2012 season Fagan signed for
St Patrick's Athletic for the 2012 season, replacing
Danny North as Pats' number 9. Fagan started off well at his new club, receiving the man of the match award at home to
Cliftonville, for his superb link up play in the
Setanta Sports Cup First Round Second Leg at
Richmond Park. Although he was suspended for the first three games of the season, Fagan was eligible to play in the
Leinster Senior Cup, and he played the full game against
Phoenix and scored his first goal for Pats after three minutes. He made his league début away to his old club
Bohemians as a second-half substitute. Fagan's first league start for the
Saints also marked his first league goal when he scored a 43rd-minute equaliser in the
Dublin derby against rivals
Shelbourne at
Tolka Park. Fagan continued his excellent form when he was one of the main players in Pats' 5–1 demolition of rivals
Shamrock Rovers, he set up
Christopher Forrester's second goal and scored his side's fourth and fifth goals when he rounded Rovers goalkeeper
Oscar Jansson to finish and the fifth was a header into the empty net after a good ball by
Jake Kelly. His backheeled assist for
Chris Forrester's famous scooped goal made it on to the 'Showboat' section of the hugely popular
Soccer AM. Fagan continued his excellent form with the opening goal in a 2–0 win over
U.C.D. More success followed for Fagan when he scored a brace against
Bray Wanderers at the
Carlisle Grounds although unfortunately the Saints had two points taken from them by a 94th-minute
Jason Byrne equaliser in a 3–3 draw. He scored his seventh league goal of the season when he opened the scoring away to
Monaghan United in a 4–0 thrashing. Goals 9 and 10 of the season came against his old club
Bohemians when he tapped in an 82nd-minute equaliser and a 94th-minute header in a 2–1 win. Fagan scored a vital goal in a 1–0 win over
Íþróttabandalag Vestmannaeyja (ÍBV) from
Iceland, when he volleyed in a
Ger O'Brien cross. He scored a vital away goal against
NK Široki Brijeg at
Stadion Pecara in Bosnia and Herzegovina in a 1–1 draw. He also scored the winner in a 2–1 win in the 105th minute in the second leg, making it four goals in his last four games in the
Europa League and earning Pats a tie with
Hannover 96 from Germany. He received the
League of Ireland Player of the Month award for July for his wonderful European exploits. Fagan continued to excel with Pats and he scored the winner in a 1–0 win away to
Cork City at
Turners Cross to make it to the 10 goal mark in the league. Fagan was in excellent for towards the end of the
2012 season, scoring away to
Shelbourne in a 2–0 win, away to eventual champions
Sligo Rovers in a thrilling 3–2 loss and at home to
Cork City on the final day of the
league season in a 1–0 win to secure qualification to the
2013–14 Europa League. On 6 November 2012, Fagan made it 2–2 with an 87th-minute equaliser in the
2012 FAI Cup final at the
Aviva Stadium against
Derry City but unfortunately for him and everyone connected with the club, Pats lost 3–2 after extra time to extend their cup-hoodoo to 52 years and 7
FAI Cup Final losses since a cup triumph.
2013 season Fagan started off the 2013 season playing well but lacking goals and as a result of this, he lost his place in the team to
Anto Flood. Fagan won himself a penalty in the 85th minute away to
Cork City, but his kick was easily saved by Mark McNulty in goal. On 6 May 2013, Fagan made his 50th appearance for the Saints in all competitions, when he came on from the bench away to
Drogheda United in the 76th minute and after just five minutes he scored a tap in from a
Ger O'Brien cross, ending a 14-game goal drought and putting the Saints 1–0 up. Drogheda equalised in the 90th minute but straight from tip-off, Fagan appeared to handle the ball himself in the Drogheda box but won a penalty that
Killian Brennan scored to win the game 2–1 for Pats. This regained his place in the starting 11 in the
Dublin derby against
Shamrock Rovers, but he failed to score as Pats drew 0–0.
Anto Flood however picked up an illness so Fagan retained his place in the team for another
Dublin derby, away to
Shelbourne. Fagan didn't disappoint and scored twice as Pats cruised to a 3–0 win.
Flood returned from illness for the trip to both striker's former club
Bohemians, but Fagan beat him to the starting spot and opened the scoring after 24 minutes to make it four goals in four games for him, as Pats won 2–0 to go top of the
league. He continued his good form as he scored away to
Dundalk in a rare 2–1 loss for Pats on 14 June as well as scoring two goals against
Bray Wanderers on 28 June as the Saints won 2–0 at
Richmond Park. However, he would have to wait until 19 August for his next goal, his two goals away to
Shelbourne were enough to see
St Pat's through to the
2013 Leinster Senior Cup Final. Fagan's final goal of the season came on 26 September 2013 when he scored in the 95th minute to secure a 3–1 win against
Bray Wanderers at the
Carlisle Grounds in a vital game in the
League of Ireland title run-in. On 13 October 2013 at a packed
Richmond Park, Pats beat
Sligo Rovers 2–0 to seal the
2013 League of Ireland title, the club's ninth league title and Fagan's first trophy in senior football.
2014 season Fagan started the
2014 season brilliantly, winning another trophy in the form of the inaugural
2014 FAI President's Cup, as the Saints beat
Sligo Rovers 1–0 at
Richmond Park on 2 March 2014. He got off the mark early with his goalscoring as he opened the scoring on the opening day of the
2014 League of Ireland season away to
Cork City to earn a 1–1 draw for his side. He followed this up by scoring a 92nd-minute winner a week later in a 3–2 win at home to
UCD in the second league game of the season. Fagan brought his goalscoring tally up to three goals in three games on 22 March, when he opened the scoring against
Limerick at
Richmond Park. In July 2014, he scored the opening goal in St. Patrick's' 1–1 draw away to
Legia Warsaw in the first leg of their
2014–15 UEFA Champions League second qualifying round tie. ==International career==