Chelsea in 2018
Early career After playing for grassroots teams Bookham Colts, Leatherhead Predators and Epsom Eagles, Gallagher joined Chelsea at the age of six. In October 2018, he signed a new contract with Chelsea, contracting him to the club until June 2021. He was awarded Chelsea's Academy Player of the Year for the
2018–19 season. On 14 January 2020, Gallagher was recalled by Chelsea. On 15 January 2020, the day after leaving Charlton, Gallagher joined Championship club
Swansea City on loan for the rest of the
2019–20 season. During his time in South Wales, Gallagher was part of the Swansea team that reached the semi-finals of the
Championship play-off, where they lost 3–2 to
Brentford on
aggregate. He later said that his time at Swansea allowed him to be more creative as a player.
2020–21 season: Loan to West Bromwich Albion On 17 September 2020, Gallagher signed a new five-year contract with Chelsea, and joined fellow
Premier League club
West Bromwich Albion on loan for the
2020–21 season. On 28 November, Gallagher scored his first Premier League goal and his first goal for West Brom in a 1–0 home league win over
Sheffield United. His only other goal for the club came in a 5–1 home defeat to future club
Crystal Palace on 6 December. Gallagher was named Albion's Young Player of the Season as the club finished 19th in the Premier League and were relegated to the Championship.
2021–22 season: Loan to Crystal Palace In July 2021, Gallagher joined Premier League club
Crystal Palace on loan for the
2021–22 season. He scored two goals in a 2–2 draw with
West Ham United on 28 August 2021, his first goals for Palace. In November, Gallagher was subjected to
homophobic chants from a group of
Leeds United fans; the club issued a statement which condemned this. By the start of December, he had six goals and three assists for Crystal Palace, the most of any Premier League player aged 21 or under. On 15 April 2022, he was prevented by parent club Chelsea from playing against them in the FA Cup semi-final; Chelsea manager
Thomas Tuchel apologised for doing so. Chelsea went on to defeat Palace 2–0. in 2021 During his season with Palace, Gallagher was described by
The Daily Telegraph as "one of the Premier League's most vibrant talents" and "a key player for Patrick Vieira", who was "thriving in his box-to-box role". For his performances with the club, he was later named Crystal Palace's
Player of the Season.
2022–23 season: Return to Chelsea In July 2022, ahead of the
2022–23 season, Gallagher said he was determined to make a first-team breakthrough at Chelsea. On 6 August 2022, he made his Chelsea debut as a substitute in a 1–0 away win against
Everton in the
Premier League. He made his first start for the club in a 3–0 away loss to
Leeds United on 21 August. In the following match, a 2–1 win over
Leicester City at
Stamford Bridge on 27 August, he received his first career
red card for two bookable offences. On 14 September, he made his
UEFA Champions League debut as an 81st minute substitute for
Mateo Kovačić in a 1–1 draw with
RB Salzburg in the
group stage. On 1 October, Gallagher scored his first goal for Chelsea, a 90th-minute winner in a 2–1 away victory over his former club, Crystal Palace. In 2023, Gallagher scored further goals against
Brighton & Hove Albion in April and
Bournemouth in May to end his first season as a Chelsea first team player with three goals in 45 appearances. His goal against Crystal Palace was later awarded Chelsea's Goal of the Season on 28 May.
2023–24 season: Captaincy and final season Ahead of the
2023–24 season, Chelsea rejected a bid for Gallagher from
West Ham United. On 31 August 2023, Gallagher
captained Chelsea for the first time, in a 2–1
EFL Cup victory over
Wimbledon. He captained the team for the first time in a league match on 17 September as Chelsea drew 0–0 with Bournemouth. Gallagher went on to regularly serve as captain throughout the season amidst injuries to regular captain
Reece James and vice-captain
Ben Chilwell. On 7 February 2024, he scored his first goal of the season in an
FA Cup fourth round
replay win at
Aston Villa. In the following match, he scored his first two Premier League goals of the season in a 3–1 away victory over his former club Crystal Palace on 12 February. On 25 February, he was in Chelsea's starting line-up for the
2024 EFL Cup final against
Liverpool at
Wembley. He played the full 90 minutes of regular time and another seven minutes of
extra time before being substituted for
Noni Madueke in the team's eventual 1–0 loss. He scored his first home goal of the season in the fifth minute of a 4–3 win over
Manchester United on 4 April. At the end of the 2023–24 season, it was reported that Gallagher could leave Chelsea. Ahead of
Euro 2024, Gallagher insisted he was focusing on the tournament rather than his club future. In July 2024, Chelsea entered into talks with Spanish club
Atlético Madrid regarding a potential transfer, and later accepted a transfer offer. After being told he would not be a regular starter under new Chelsea manager
Enzo Maresca, he later agreed to the move. The transfer later stalled, and Gallagher began training away from Chelsea's first team. However, later that month, the potential transfer was back on, with
João Félix moving in the other direction as part of the deal.
Atlético Madrid On 21 August 2024, Atlético Madrid announced that they had signed Gallagher on a five-year contract. The transfer fee was reported by
The Guardian to be in the region of £34 million. The transfer was met with mixed reactions from Chelsea fans.
2024–25 season Gallagher made his official debut for Atlético as a 58th-minute substitute for
Rodrigo Riquelme in the team's
2024–25 La Liga season opener against
Girona at the
Estadio Metropolitano on 25 August. He scored the opening goal in a 3–0 win over
Valencia on 15 September, becoming the first Englishman to score a league goal for the club. Seven days later, he scored his second La Liga goal in a 1–1 draw with
Rayo Vallecano. His early performances for Atlético were praised, with the
BBC describing him as "an unqualified success so far". On 12 March 2025, Gallagher scored his first
UEFA Champions League goal in the opening minute of the second leg of the
Round of 16 matchup against
Real Madrid to level the aggregate score at 2–2. Atlético went on to lose the tie in a
penalty shootout after there were no further goals during the match. In June 2025, Gallagher was part of the Atlético Madrid squad that competed at the
2025 FIFA Club World Cup in the United States. He appeared in all three matches as Atleti were eliminated at the group stage, losing 4–0 to
Paris Saint-Germain and beating
Seattle Sounders and
Botafogo 3–1 and 1–0 respectively.
2025–26 season In his second season at Atlético, Gallagher was primarily used as a substitute by coach
Diego Simeone. Despite his lack of starting opportunities, Gallagher was one of only two players to appear in all 27 of Atleti's matches in
2025–26 prior to his departure from the club. On 4 November 2025, he scored the second goal of a 3–1 win over
Union Saint-Gilloise in the
UEFA Champions League. On 21 December, he scored his second
La Liga goal of the season, and third in all competitions, after replacing the injured
Nicolás González in a 3–0 win away at Girona. Gallagher's final appearance for Atleti came in the 2–1
Supercopa de España semi-final loss to
city rivals Real Madrid. He played the first 45 minutes in the match played in Jeddah, Saudi Arabia on 8 January 2026.
Tottenham Hotspur In January 2026, Gallagher was linked with a transfer to either
Aston Villa or
Tottenham Hotspur. On 14 January 2026, Gallagher signed with Tottenham Hotspur for a reported fee of £35 million. He described the decision to sign as being "very easy". ==International career==