His form with his local club was good enough to earn a move to fellow Dublin club Lourdes Celtic where he played alongside future League of Ireland players including a future St Patrick's Athletic teammate Derek Foran, as well as earning his first Republic of Ireland Underage callups.
Bermingham made his first start for the club in a League of Ireland Cup game against Kildare County later that month and was a first team regular from then, solving UCD's long-term search for a left back.
[14] He was part of the side that reached the 2010 Setanta Cup Final, including playing the full 90 minutes as Pat's were defeated 1–0 by Bohemians at Tallaght Stadium on 15 May 2010.
[24][25] He made 2 appearances in the Leinster Senior Cup which Pat's won on 10 October 2011, beating Bohemians in the final at Dalymount Park, resulting in a first career medal for Bermingham.
[26] Pat's finished up in 4th place, securing UEFA Europa League football for the next season,[27] while they were once again knocked out of the FAI Cup at the Semi Final stage after a replay, this time against Dublin rivals Shelbourne.
[5] After making 52 league appearances for the Saints over two seasons, Bermingham signed a new one-year contract with the club under new manager Liam Buckley on 21 January 2012.
[28] The season was a success with the team playing excellent football under their new manager, resulting in some memorable performances including a famous 5–1 win over Shamrock Rovers.
[29] They continued their form into their UEFA Europa League campaign, once again knocking out ÍBV of Iceland,[30][31] before facing NK Široki Brijeg of Bosnia and Herzegovina, drawing 1–1 away[32] and winning 2–1 at home[33] in a game in which made his 100th appearance for the club on 26 July 2012.
[43] He played the full 90 minutes on 9 August 2013 as his side recorded a famous 4–0 win over Shamrock Rovers at Tallaght Stadium, with Conan Byrne scoring all 4 goals.
[46] In the 31 games it took them to win the league, Pat's defence of Bermingham, Ger O'Brien, Conor Kenna, Kenny Browne and goalkeeper Brendan Clarke amazingly conceded just 15 goals.
[47] On 20 October 2013, he was an unused substitute in the 2013 Leinster Senior Cup Final as his side lost 1–0 to Shamrock Rovers,[48] having lifted the league trophy just 42 hours previously, following a 1–1 draw with Derry City.
[52] On 16 July 2014, he made his first appearance in the UEFA Champions League, assisting Christy Fagan's goal in a 1–1 draw away to Legia Warsaw at the Polish Army Stadium.
[60][61] Bermingham made 3 appearances in the League of Ireland Cup but missed the final on 19 September 2015 due to suspension, as his side beat Galway United on penalties to claim the trophy.
[64] He featured in every game of the club's UEFA Europa League campaign once again, as they knocked out Jeunesse Esch of Luxembourg[65][66] before losing 2–1 on aggregate to Dinamo Minsk of Belarus.
His first goal of the season came on 31 January 2017 when he opened the scoring in a 4–0 Leinster Senior Cup win over Bray Wanderers at the Carlisle Grounds.
[74] He helped his side earn a draw away to Limerick on 24 June 2017, when he scored to reduce their 2-goal deficit to just one, before Conan Byrne equalised with 15 minutes to play.
[75] On 25 September 2017, he opened the scoring with a header in a vital 2–0 Dublin derby win over Shamrock Rovers as the relegation battle continued.
[85] On 13 July 2019, Bermingham faced Premier League side Chelsea in a friendly at Richmond Park, marking FIFA World Cup Winner Pedro.
[101][102] His final appearance in professional football came in a 4–0 win over Shelbourne on 6 November 2022, with Bermingham coming on at half time as a substitute before being subbed off in the last minute of the game to a guard of honour from his teammates.
[109] Bermingham has a keen interest in horseracing and was part owner of Cubomania, a horse that was ridden by Davy Russell at the 2019 Cheltenham Festival.
[111] After winning the 2021 FAI Cup, Bermingham revealed that his first child had been born just 2 days before the Final, stating that "all of my dreams came true in a weekend.