After a spell on loan with Brentford the following season, he later became the capital club's first choice goalkeeper, winning two FA Cups and being the joint recipient of the 2013–14 Premier League Golden Glove alongside Petr Čech.

At international level, Szczęsny earned 84 caps for Poland between his debut in 2009 and 2024, and was included in the nation's squad as it co-hosted UEFA Euro 2012; he would later participate in three more editions of the tournament (2016, 2020 and 2024), as well as two FIFA World Cups (2018 and 2022).

[8] Szczęsny appeared on the first-team bench for the first time during the Premier League match against Stoke City on 24 May 2009, remaining unused as the team concluded their season with a 4–1 victory at the Emirates Stadium.

On 22 September 2009, he made his first-team debut in the Football League Cup third round, keeping a clean sheet in a 2–0 home win against West Bromwich Albion.

[23] He signed a new long-term contract on 11 November 2010, thanking both his father and his goalkeeping coach, Josh Phelan, for helping him progress in his breakthrough season.

[24][25] Szczęsny made his Premier League debut in the 1–0 loss to Manchester United at Old Trafford on 13 December 2010, deputising for Łukasz Fabiański and Manuel Almunia, who both missed the match through injury.

[citation needed] Following Szczęsny's form after playing consecutive Premier League matches, Arsène Wenger confirmed that he would remain Arsenal's first choice goalkeeper, stating, "he's done nothing for me to take him out.

[28] On 27 February, Szczęsny let in a last-minute Birmingham City winner in the League Cup Final; a header from Nikola Žigić caused confusion between Szczęsny and defender Laurent Koscielny where the latter pulled out of a clearance at the last minute causing the former to lose control of the ball, which rolled right into the path of Birmingham forward Obafemi Martins, who converted from close range.

On 24 August, Szczęsny made a vital penalty save in the 59th minute of play against Antonio Di Natale in the second leg of the Champions League qualifying round.

[citation needed] On 20 April 2013, Szczęsny returned to the team in a Premier League match at home to Everton due to a rib injury sustained by Fabiański.

[citation needed] Szczęsny had a testing time in the opening fixture of the 2013–14 Premier League season, as Arsenal lost 3–1 to Aston Villa.

He also made two crucial saves to help preserve Arsenal's 1–0 lead away to Crystal Palace in October,[36] as well as keeping two consecutive clean sheets in vital wins over Liverpool[37] and Borussia Dortmund in the Champions League.

[38] In a November 2013 match against Manchester United, Szczęsny received lengthy treatment following a head-to-head injury with Phil Jones, but finished the game after Arsenal manager Arsène Wenger allowed him to continue.

Wenger said he would have substituted for Szczęsny if instructed by the team doctor, but added, "No, nobody told me anything about him," when asked if medical staff had cleared the goalkeeper to play.

[39] Tottenham coach André Villas-Boas was heavily criticised the previous week for keeping concussed keeper Hugo Lloris in a match against Everton.

[citation needed] Szczęsny conceded a penalty and was sent off in a 4–1 Champions League home win against Galatasaray on 1 October 2014 for a professional foul on Burak Yılmaz.

[48] Szczęsny was selected to start in the 2015 FA Cup Final, keeping a clean sheet in a 4–0 victory over Aston Villa at Wembley Stadium.

[51] Szczęsny dislocated a finger during Roma's opening Champions League match against Barcelona after clashing with Luis Suárez, an injury that kept him out for six weeks.

In an interview with Il Tempo newspaper, Szczęsny stated that he felt that his season with Roma had been positive, and credited his experience training and playing in Italy under manager Luciano Spalletti and goalkeeper coach Nanni as being extremely beneficial to his development.

[57] During the summer of 2016, Roma also signed Brazilian goalkeeper Alisson Becker from Internacional, meaning that Szczęsny would face competition for a starting spot in the team.

[59] On 9 September 2017, Szczęsny made his first appearance for Juventus, achieving a clean sheet as he started in their third match of the season, a 3–0 home win over Chievo in Serie A.

[90][91] On 2 October 2024, Szczęsny returned to football just over a month after announcing his retirement, signing for La Liga club Barcelona on a contract until the end of the 2024–25 season.

[92] He was chosen to replace first choice goalkeeper Marc-André ter Stegen, whose season was cut short due to long term injury.

[citation needed] In October 2009, new manager Franciszek Smuda sent Szczęsny his first call up to the full national side, for the friendly matches against Romania and Canada.

[100] Szczęsny had a strong performance against Germany on 6 September 2011, making eight critical saves in a 2–2 draw; this earned him praise from former German international goalkeeper Oliver Kahn.

[104] Nonetheless, Poland made it to the quarter-finals, with former Arsenal teammate Łukasz Fabiański in goal, where they were eliminated from the tournament on penalties by eventual champions Portugal.

[116] On 26 March 2024, in the Euro 2024 qualifying play-off final, Szczęsny saved the deciding penalty from Daniel James during the shoot-out, which Poland won 5–4 against Wales after a goalless draw, sending his country through the tournament.

[123] During his time with Arsenal, Szczęsny earned a reputation as a tall, promising, and talented goalkeeper, who possessed significant athleticism, as well as strong reflexes, agility, shot-stopping abilities, distribution, and a good mentality, but who was also inconsistent; as such, he occasionally came under criticism in the media over technical mistakes or errors in judgement, in particular on crosses, and for his lack of development during his time with the club,[124][125][126][127][128] as well as his lack of discipline off the pitch, including an incident in which he was reportedly fined by the club after being caught smoking in the showers.

[47][129] Regarding Szczęsny's error–prone performances during his time in England, former Arsenal goalkeeper David Seaman commented in 2013 that the Polish keeper needed to become stronger mentally in order to retain his place in the first team.

[137] Szczęsny's former goalkeeping coach at Roma, Nanni, praised him in 2017 for his dedication in training, and for his ability to overcome his weaknesses and develop his all–round game, noting that he initially struggled to get to ground quickly to parry the ball and deal with low shots upon his arrival at the club, but that he improved significantly in this area under his tenure; he also lauded the keeper for his intelligence, cool demeanour, and calm composure in goal, as well as his ability with the ball at this feet.