In July2000, he joined a Belgian club Royal Antwerp, and became the first South Korean footballer who scored double digits in a European league during a season since Cha Bum-kun. After successful season with Royal Antwerp, he moved to Anderlecht. He scored a hat-trick in the space of 12 minutes in the 2001 Belgian Super Cup, and he scored the first South Korea goal of the qualifying round of the UEFA Champions League. He also won the 2003–04 First Division with Anderlecht.
In August 2004, Seol moved to England, joining Championship club Wolverhampton Wanderers. The Wolverhampton coach at the time, Glenn Hoddle, preferred Seol as one of his first-choice forwards, using him in various roles including striker, attacking midfielder and winger of both sides. Disappointed with the failure of Wolves to win promotion from the Championship, Seol sought a move to the Premier League following the 2006 FIFA World Cup, despite having two years of his contract left. He was reported as saying "At this stage, I'm frustrated not to be in the Premiership. I think there will be some good news after the World Cup."
Reading
Seol eventually joined newly promoted Premier League club Reading on 12 July 2006 for a fee of £1 million. On 16 September 2006, he scored his first Premiership goal as Reading won 2–1 at Sheffield United. On 1 October 2006, he scored his second goal for Reading against West Ham United, proving to be only goal of the match. He was voted by Reading fans as the official Player of the Month for August 2006 by showing great performances early in the season, and was ranked 11th in the player rankings of the Premier League after the seventh round. His third goal for Reading, his first at home, came on 18 November 2006 in the 2–0 win against Charlton Athletic. He scored his fourth goal against Blackburn Rovers, the last game of the season.
Fulham
Seol left Reading for Fulham on 31 August 2007 for an undisclosed fee on a three-year contract, with Liam Rosenior going the other way. Reading boss Steve Coppell admitted that strained relations between him and Seol led to the move. He did not score his first goal for Fulham during his first season. On 16 August 2008, he scored his first goal against Hull City, but Fulham lost 2–1. On 14 January 2009, he had signed an initial 6-month loan move to Al-Hilal in Saudi Arabia with a view to moving permanently. However, he stated that he desired to stay at Fulham to win his place in the squad, and he went on to score his second goal for the club against FK Vetra in the Europa League. On 15 January 2010, It was announced that his contract with Fulham had been cancelled by mutual consent. After the last career in the K League, Seol announced his retirement on 2 March 2015 in order to become interim manager of Sungkyunkwan University. A retirement ceremony took place in a friendly match of South Korea and Jamaica on 13 October 2015.
International career
Seol played in his first World Cup in front of his home crowd, South Korea being co-hosts with Japan for the 2002 FIFA World Cup. He was a key member of the squad during the tournament, memorably scoring the equalizer against Italy in the round of 16. He was nominated for the 2002 Ballon d'Or in that year.
Managerial career
On December 26, 2019, Seol was appointed as manager of Gyeongnam FC.
