Early career De Jong began his football career at the
Doetinchem amateur club DZC'68 and was scouted by
De Graafschap, when he was 12. He grew up in
Doetinchem and graduated from the same school (het Rietveld Lyceum) as
Guus Hiddink,
Paul Bosvelt and
Klaas-Jan Huntelaar, which grants him immediate university access (he has considered studying economics). He played with De Graafschap until 2005, when he was picked up by the
Ajax youth academy. His
Eredivisie debut was also as a substitute, away at
Sparta Rotterdam, where he scored an injury-time equaliser. In
2007–08, he was one of the youngest players and the only player under age 20 to play more than 20 games. On 16 January, just before turning 19, he extended his contract with Ajax to June 2013. He picked up an injury against
Willem II, missing two months. This made him miss all the games from 16 March onward, including matches against
PSV,
Twente and
Heerenveen. He recovered from this injury in early April, returning fit for the match against De Graafschap. Although he did not start that game, he was substituted on in the 81st minute for
Edgar Davids. During the beginning of the
2009–10, De Jong was often used as an impact substitute and only started in
UEFA Europa League games. He eventually earned his place in the starting XI. In January, he scored the winner in the last few minutes of extra time to send Ajax through to the semifinals of the
KNVB Cup. On 21 February, he scored a brace against
Vitesse in a 4–0 win to keep Ajax's push for
UEFA Champions League qualification alive. On 15 May 2011, De Jong played in the title-decider game against Twente and helped Ajax win its first—and 30th overall—
Eredivisie title since 2004 by scoring two goals, sealing the 3–1 victory. In the
2011–12 season, De Jong often found himself playing as a striker due to several injuries to the natural strikers on the Ajax roster. On 11 April 2012, he scored a hat-trick as Ajax defeated ten-man Heerenveen 5−0 in the 29th league game of the season and moved three points clear of second-placed
AZ in the
Eredivisie table. De Jong scored both goals against
VVV Venlo on 2 May 2012, helping Ajax retain the Eredivisie title. In the summer of 2012, following the departure of teammate and captain
Jan Vertonghen to
Tottenham Hotspur, De Jong was appointed as the new Ajax captain. He was in fine form in the
2012–13 Champions League, scoring once at home to English Champions
Manchester City and scored twice away from home in the same fixture on 6 November 2012. On 17 March 2013, De Jong netted a brace in a 2–3 defeat of AZ at the
AFAS Stadion in
Alkmaar. On 27 July 2013, De Jong scored a goal in the 107th minute as Ajax defeated AZ by a score of 3–2 in the
2013 Johan Cruyff Shield. He scored a goal in either half as Ajax defeated
NEC 3−0 on 10 November in the 13th round of
Eredivisie play.
Newcastle United On 1 July 2014, De Jong signed a six-year deal with
Newcastle United for a fee believed to be around £6 million. Following his signing for the club, De Jong was named as a vice-captain by manager
Alan Pardew. He made his competitive debut as a 70th-minute substitute in a
Premier League match against
Aston Villa on 23 August 2014. He injured his right thigh during training in early September, ruling him out for "a number of months". De Jong was due to make his return to the Newcastle first team in February 2015, but he was sidelined for a further eight weeks due to a collapsed lung, a condition he had previously experienced while at Ajax. Upon his return to the team, De Jong scored his first Newcastle goal in a 3–2 loss against
Swansea City on 25 April 2015. De Jong started for the club in a 4–1 victory in the
League Cup at
Northampton Town, scoring Newcastle's second goal, his second for the club. In January 2016, De Jong was sidelined for two weeks in a freak accident in which one of his
contact lenses was pushed into his eye, threatening his sight.
PSV (loan) On 22 August 2016, Newcastle confirmed that De Jong had moved to PSV on a season-long loan. On 11 December, he scored his first goal for PSV against
Go Ahead Eagles four minutes after coming off the substitutes' bench in the 64th minute. The goal helped PSV close to within three points of
Feyenoord and Ajax, which were joint top of the
Eredivisie table. Asked about his longer-term future, De Jong said that it would be ideal if Newcastle "are promoted first and then I return to play in the
Premier League", which eventually proved successful on 25 April 2017 after beating
Preston 4–1.
Return to Ajax On 28 August 2017, it was announced that de Jong would return to Ajax, signing a three-year contract with the Amsterdam club.
Sydney FC (loan) On 23 August 2018, de Jong joined
A-League side
Sydney FC on a season-long loan deal. He was part of the team that won the
2019 A-League Grand Final.
FC Cincinnati de Jong joined
MLS side
FC Cincinnati on 20 February 2020. He was released by Cincinnati at the end of their 2020 season.
SC Heerenveen On 4 December 2020, de Jong returned to the Netherlands with
Eredivisie side
SC Heerenveen.
De Graafschap On 16 June 2022, de Jong signed a one-year contract with
De Graafschap with an option for an additional year. The move meant a return to his boyhood club. On 18 May 2023, he announced his intention to retire after the final match of the season the following day. ==International career==