Hull City Cooper joined his hometown club
Hull City in 2002 at under-12 level. During the
2007–08 season, he was given the number 37 shirt but failed to make any appearances as the Tigers went on to win promotion to the
Premier League for the first time in their history. He made his debut as 16-year-old for the club against
Swansea City in the
League Cup on 26 August 2008 and featured as an unused substitute in their
Premier League defeat to
Wigan Athletic four days later after signing his first professional contract. A year later, he would make his first Premier League start on 26 September 2009 at
Anfield in a 6–1 defeat to
Liverpool. Over the following three years, Cooper would find his opportunities limited at Hull and spent brief periods out on loan at
Carlisle United and
Huddersfield Town in 2011. He briefly returned to the first team under
Nick Barmby to form a solid partnership with
James Chester in March 2012 for the rest of the season following an injury to
Jack Hobbs. When Barmby departed for
Steve Bruce in the summer of 2012, he was replaced by the new manager's son
Alex.
Chesterfield Cooper joined
League Two side
Chesterfield in November 2012. He made his debut in a 6–1 win over
Hartlepool United in the
FA Cup, and scored on his league debut two weeks later in a 2–1 victory over
Oxford United. The
2012–13 season was Cooper's first year of playing regular professional football, making 31 appearances in all competitions as the Spireites narrowly missed out on a play–off spot. The
2013–14 would prove to be a memorable campaign for both Cooper and Chesterfield under manager
Paul Cook. The club reached the
2014 Football League Trophy Final and played at
Wembley Stadium, but ultimately lost 3–1 to
Peterborough United in front of more than 35,000 fans. In the league, Cooper formed a formidable partnership with
Ian Evatt as the team won the division and were promoted to
League One. At the end of the season, Cooper was named in the
PFA Team of the Year along with three other Chesterfield players.
Leeds United Early years and captaincy season Cooper came to the attention of
Leeds United after impressing
sporting director Nicola Salerno in a 2–2 preseason draw at the
b2net Stadium in the summer of 2014. After weeks of negotiations, Leeds agreed a deal for £600,000 plus add-ons relating to appearances, a future sale and promotion; with Cooper joining the club on 13 August. (After winning promotion to the
Premier League in 2020, the Spireites received an additional £150,000 from the sale.) He made his debut three days later at home to
Middlesbrough in a 1–0 win, before being made
club captain by
Neil Redfearn midway through his first season. He would struggle for consistency under a succession of managers, losing his starting place to
Sol Bamba and later to
Pontus Jansson, but would still go on to make over 100 appearances during his first four seasons with the club. During a period of 30 games between 2017 and 2018, Cooper was sent off three times and received another six game ban for a stamp on
Reading defender
Reece Oxford. His propensity to be a liability in games earned him the disparaging nickname 'League One Liam' among Leeds fans at the time, but Cooper remained a highly respected captain amongst his teammates. He kept hold of the captaincy during
Thomas Christiansen and
Paul Heckingbottom's time as manager in the
2017–18 campaign, who would be his 7th and 8th manager respectively at the club in less than four years.
Bielsa and promotion Cooper retained the captaincy after the shock appointment of the world renowned
Marcelo Bielsa as Head Coach in the summer of 2018. In Bielsa's first game, he scored the third goal in a comprehensive 3–1 victory over promotion favourites
Stoke City, as Leeds ascended to the top of the Championship by Christmas. Leeds would eventually lose out on automatic promotion to
Norwich City and
Sheffield United as their form dipped in the second half of the 2018–2019 campaign, before losing 4–3 on aggregate to
Derby County in the play-offs. In spite of a disappointing end to a season that had long looked so promising, Cooper was widely perceived to be one of the most improved players in the team under the new head coach, and was included in the
EFL Championship Team of the Season,
EFL Team of the Season, as well at the
PFA's Championship Team of the Season with teammates
Pontus Jansson and
Pablo Hernández. The
2019–2020 marked Leeds' centenary year and Cooper's sixth season with the club. He would sign a new five-year deal with the club in September, and would be present at
The Best FIFA Football Awards 2019 to collect the
FIFA Fair Play Award on behalf of Bielsa and the Leeds United team for allowing
Aston Villa to score an uncontested goal in the previous season. On the pitch, the team's nine–point lead at Christmas in the automatic promotion zone was completely eroded by the beginning of February after a run of four defeats in five games. With questions again being asked of Leeds' ability to maintain the form over the course of a full season, Cooper would score a crucial equaliser in a 1–1 draw in the following game against promotion rivals
Brentford. It would later transpire that Cooper's son had been in hospital for three days prior to the game and there were doubts over whether he would play at all. The result proved to be a catalyst for the Yorkshire club's season, as they went on to win their next five games with Cooper being part of a defence that would also keep five clean sheets, taking the team back to the summit of the table and reestablishing a seven–point lead in the automatic promotion places. The momentum building around the club with only nine games remaining would be halted six days later when the season was suspended due to the
COVID-19 pandemic. The season would resume behind closed doors three months later in June, with Leeds' five match winning run coming to an immediate end with a 2–0 defeat to
Cardiff City. Leeds would only drop two further points from the remaining eight games, as Leeds secured promotion to the
Premier League on 17 July after West Yorkshire rivals
Huddersfield Town beat
West Bromwich Albion 2–1, and won the Championship title the following day after Brentford failed to beat Stoke City. Cooper became the first Leeds United captain to win promotion since
Gordon Strachan in 1990 and lifted the Championship title on 22 July after a 4–0 win over
Charlton Athletic on the final day of the season, immortalising himself in the club's history. He would also retain his place in the
PFA Team of the Year.
Premier League Cooper missed Leeds' first Premier League game for 16 years in a 4–3 away defeat to
Liverpool on the opening day of the season after picking up an injury. In the following match, he made his first Premier League start since September 2009 in a 4–3 win over
Fulham. The period between stands at 10 years, 359 days was a league record for the greatest length of time between starts. The following game against
Sheffield United also marked his 200th appearance with the club and the first player to reach that number of games since
Luciano Becchio in 2012. that have made over 200 appearances for the club, including teammate
Stuart Dallas who also hit the milestone later in that season.
Return to the Championship On 6 August 2023, Cooper scored the team's first goal on the opening day of
Leeds' 2023–24 Championship league campaign, a 2–2 home draw with
Cardiff City, injuring his knee in the process, which kept him out of the team until his 20 September return as a second-half substitute against
Hull City. On 11 September 2024, Cooper left Leeds permanently, ending his 10-year stay with the club as captain.
CSKA Sofia On the same day, Cooper moved to Bulgaria, signing for
Bulgarian First League club
CSKA Sofia.
Sheffield Wednesday On 17 November 2025, Cooper returned to England, joining Championship side
Sheffield Wednesday on a free transfer running until the end of the
season. He made his debut the following weekend on 23 November in the
Steel City derby against local rivals
Sheffield United, where he came on as a first half substitute for teammate
Dominic Iorfa, which later saw the Owls lose 0–3 to the latter. He scored his first goal for Wednesday on 21 December, rifling home a failed clearance from a free-kick against
Ipswich Town. ==International career==