Willem II De Jong signed his first professional contract with Willem II on 1 August 2013, aged sixteen.
Ajax in 2019 At the beginning of the season, on 22 August 2015, Ajax purchased De Jong. He signed a four-year contract, for a symbolic €1 fee which included a 10% sell-on bonus. On 23 August 2015, he was loaned back to Willem II until 31 December 2015. During this time he made one substitute appearance in an Eredivisie match against
PEC Zwolle.
2016–2019: Development and first-team regular For the first two years at Ajax, De Jong was in and out of the first team squad. After returning to the club in January 2016, de Jong made 15 appearances in the
2015—16 Eerste Divisie for
Ajax II. He primarily played in the centre of a three-man midfield and scored two goals. The following year, he was awarded the
2016–17 Eerste Divisie's Talent of the season award for his performances with Ajax II for whom, he made 31 first team appearances and played as a central, and defensive, midfielder. He made his senior debut against
Sparta Rotterdam coming on, in the 88th minute, for
Lasse Schöne. In total, he made four senior appearances for Ajax, and scored one goal against
Go Ahead Eagles, in the
2016—17 season. He started one game, came off the bench thrice, and was an unused substitute in 13 games. He also made his European debut and made four substitute, and three bench, appearances, in the
2016–17 Europa League. He came off the bench in the 82nd minute against
Manchester United in the
final. It was Ajax's first European final in 21 years. Aged 20, he made 26 appearances for the first team. Primarily he featured as a center-back, in a back four, alongside national teammate
Matthijs de Ligt due to the departure of
Davinson Sanchez. He also played in a three-man center-midfield. He recorded eight assists in 22 league appearances and received two yellow cards. Towards the end of the season he was injured—tendonitis, syndesmotic ligament tear, hairline crack in calf bone—and missed three months. De Jong made two substitute appearances in the
2017–18 Champions League qualification, as Ajax lost on away goals against
Nice (3–3) in the third qualifying
round. In the
2018–19 season, he primarily played in the middle of a three-man midfield. De Jong was the Eredivisie player of the month in December (2018) and February (2019)—in which he completed 354 of 390 passes and made 53 ball recoveries. Later that month he received praise from
Rafael Van Der Vaart, who said De Jong was among the best players in Europe with the ball at his feet. It is unclear whether during or prior to the beginning of the campaign he rejected an offer from Tottenham Hotspur, saying the "moment wasn't right", and wanted to play a full season in his preferred position at Ajax. De Jong achieved success, and widespread recognition, during the
2018–19 season and led Ajax to their first domestic double (league and cup) since the
2001–02 season. Ajax wrestled with
PSV Eindhoven all season for the league, and finished the last five weeks at the top of the
table. He made 51 total appearances and starred in Ajax's first leg (0–1) win over
Tottenham Hotspur in the
2018–19 UEFA Champions League semi-final at
Tottenham Hotspur Stadium—in which De Jong had the most touches by any player on the pitch (87) and an 86.2 percent pass completion rate. It was the first time Ajax made the tournament semi-final since
1997. The team eliminated Juventus (3–2 on
agg.) in the
quarterfinals and
Real Madrid (5–3 on agg.) In the second leg of the semi-final, Ajax lost 2–3 at home and were knocked out on
away goals to English club Tottenham Hotspur. De Jong was selected to the
2018–19 UEFA Champions League squad of the season and voted
the tournament's midfielder of the season.
Barcelona in 2021 On 23 January 2019,
La Liga club
Barcelona announced the signing of de Jong on a five-year contract, effective from 1 July 2019, for an initial fee worth €75 million. De Jong had transfer discussions with
Paris Saint-Germain,
Manchester City and
Manchester United before ultimately opting for Barcelona. He made his competitive debut on 16 August 2019, in a 0–1 opening day defeat to
Athletic Bilbao. He played a crucial role in the
2021 Copa del Rey final, a 4–0 win over Athletic Bilbao, scoring in the 63rd minute and assisting two further goals. On 25 November 2023, in a match against
Rayo Vallecano, he debuted as captain for FC Barcelona due to absences of
Sergi Roberto,
ter Stegen and
Ronald Araujo. In January 2024, de Jong played his 200th game for FC Barcelona in a 3–1 victory against
Unionistas in the Copa del Rey round of 16. On 24 February 2024, he scored the 11,000th goal in FC Barcelona's history in a 3–0 win against
Getafe CF. On 21 April 2024, de Jong was injured in a match against
Real Madrid. He sprained his ankle and missed the rest of the 2023–2024 season. In the 2024–25 season, de Jong was named third captain after the departure of
Sergi Roberto. The ankle injury of last season kept him sidelined until the second Champions League fixture against
BSC Young Boys in October 2024. In the 75th minute, he made his first minutes under
Hansi Flick and for the season. He found his form in the latter half of the season. He made 44 appearances across all competitions, and his performances were marked by a high passing accuracy and tactical intelligence, solidifying his position as a key player in the squad. His resurgence in form led to discussions about contract renewal, with club officials expressing a desire to extend his stay at Barcelona. On 15 October 2025, he extended his contract with the club until 2029. On 22 April 2026, he featured in his 293rd match for Barcelona in a 1–0 victory over
Celta Vigo, becoming the Dutch player with the most appearances for the club, breaking the previous record held by
Phillip Cocu. ==International career==