South Korea, a nation that values heritage greatly, has taken a major step towards recognizing the value of dual nationals as the country prepares for the 2026 FIFA World Cup.
Jens Castrop became the country's first-ever foreign-born senior international of mixed-race heritage when he debuted for the country in 2025.
Understanding the importance of searching around the globe to uncover international talent, South Korea head coach Hong Myung-bo handed brought Castrop aboard with the idea of improving the Taegeuk Warriors' player pool as much as possible heading into the coming World Cup competition.
The Sporting News details how Castrop was eligible to play for South Korea, how he decided to make the switch from his native Germany, and where he comes from on the pathway towards international football.
Who is Jens Castrop?
Jens Castrop is a midfielder who plays for Borussia Monchengladbach and the South Korea national team.
The 22-year-old has spent his entire professional club career in Germany, coming through the youth academies of Dusseldorf and Cologne before making his senior debut with FC Nuremburg in 2022.
Born in Dusseldorf, Castrop plays for the South Korean national team, making his first international appearance against the United States in a friendly on September 6, 2025.
Upon his debut, Castrop became South Korea's first-ever foreign-born player of mixed heritage. He is the first player for either the men's or women's team with this designation; women's international Casey Phair made her debut at the 2023 Women's World Cup, but does not qualify as she was born in South Korea before moving to the United States where she was raised.
Where is Jens Castrop from?
Jens Castrop was born in Dusseldorf, Germany in July of 2003.
Born to a German father and South Korean mother, Castrop began his youth career at local club Fortuna Dusseldorf.
Castrop was a part of the Germany youth national team setup at about every level from U-16 on up, appearing for the U-17, U-18, U-19, U-20, and U-21 sides. He would file a one-time switch to represent South Korea, which was approved by FIFA in August of 2025.
Jens Castrop ethnicity, parents
Jens Castrop was born to a German father and South Korean mother.
The German-born midfielder said in an interview with the Korea Times that his father was "very shocked" at his decision to switch to represent South Korea internationally, but said his parents are "very proud and happy as long as I am here."
His mother, Su Yeon-ahn, grew up in South Korea and earned a landscape architecture degree at Seoul National University before moving to Germany in 1996. There she met her husband, a lawyer, and they settled in Dusseldorf where they had three children, all boys.
"I always told Jens, ‘Your roots are Korean, and you must have a Korean identity,'" Su said in an interview before Castrop's international debut.
Where did Jens Castrop start his career?
Jens Castrop began his youth career at his hometown club of Fortuna Dusseldorf, before leaving in 2015 to join local rival Cologne.
In 2022 he joined second-tier side Nurnberg on loan for 18 months, where he made his professional club debut on February 12 in a 4-1 defeat to Karlsruher.
After joining Gladbach in the summer of 2025, Castrop made his Bundesliga debut on August 24, coming off the bench for seven minutes in the season-opener against Hamburg.
35 &179 - Jens Castrop is one of only seven midfielders who registered 30+ successful tackles (35) and 170+ progressive carries (179) in 2024/25 2. Bundesliga. Engine. pic.twitter.com/7qpMRhvYUM
— OptaJoon (@OptaJoon) August 25, 2025
Why did Jens Castrop switch allegiance to South Korea?
Jens Castrop said that "it was a very tough decision," to decide to represent South Korea internationally, but that "you have to listen to your heart, and my heart said I want to play for Korea, and that's why I'm very proud that I'm here now."
His mother added: "My son's heart is in Korea. It is Korean, no matter what. He does not spare himself; he has a strong sense of discipline, he restrains himself from doing things. When he has free time, he walks his dog or goes fishing instead of going to parties. He focuses on football."
However, it's also likely that he saw a much better pathway towards international minutes with the South Korean national team than with Germany, where the senior level of international football is highly competitive. While Castrop was a regular in the German youth national team setup, he would have faced significant competition for senior minutes, especially in the near future ,with the likes of Leon Goretzka, Josh Kimmich, Aleksandar Pavlovic, and others entrenched in midfield positions.
Becoming a South Korean citizen for eligibility purposes comes with significant risk of personal sacrifice. All able-bodied South Korean men are required to complete a minimum of 21 months of military service by the age of 28.
This includes dual nationals, who are eligible to be drafted if they stay in Korea for more than six months in one year or engage in 60 days or more of "economic activity" before turning 37.
However, there still could be a way out for Castrop. The government awarded the entire South Korea squad, which included superstar Son Heung-Min, an exemption from military service after they won the gold medal at the 2018 Asian Games.
FIFA rules for switching international allegiance
While there are exceptions, the general rule for international football is that players are eligible to represent any nation for which they hold a valid passport.
In general, a player who makes one competitive appearance for a senior national team is locked in to appearing for only that country throughout the rest of their career.
However, as of FIFA's eligibility rules overhaul in early 2021, increased flexibility was added to the system to allow young multi-national players to take their time determining which country they wish to represent permanently.
The most effective tool for dual nationals is the one-time switch. This allows any player with the following qualifications to switch nationalities:
- Have made no more than 3 senior appearances for their previous nation while under the age of 21 (including friendlies) with the following qualifiers:
- Three years have passed since the last such appearance
- None of the appearances came at the FIFA World Cup or any continental championship (such as the UEFA European Championship or the CONMEBOL Copa America)
- They held eligibility for the new nation at the time of their prior appearances for the old nation
Castrop, having not made any senior appearances for Germany, was eligible to file a one-time switch to represent South Korea. He still had to file a one-time switch with FIFA due to his appearances for Germany at the youth level.
Jens Castrop career teams timeline
After making his professional debut for Nurnberg in the 2.Bundesliga in 2022, he joined Borussia Monchengladbach in the summer of 2025 on a transfer worth €4.5 million, signing a four-year contract.
Castrop made 92 total appearances for Nurnberg before the move, scoring seven goals and assisting nine more.
He scored his first Bundesliga goal with Gladbach in a wild 6-4 defeat to Eintracht Frankfurt on September 27, just five matches into his top-flight career. Gladbach found themselves 5-0 down at halftime and 6-0 down after 47 minutes, but clawed back to make a game of it, with Castrop scoring the first for his side in the 72nd minute.