Yun made his debut for Jeonnam Dragons in 2009 and went on to make a total on 86 appearances for the side.[3]
QPR
Yun signed for Queens Park Rangers on the 30 January 2013 for an undisclosed fee on a three-and-a-half-year deal.[4]
Yun did not make a senior appearance for QPR in his first season with the club, in which they were relegated from the Premier League. However, he was included in the match day squad as a substitute for the first game of the 2013–14 Championship season before making his first league start of the campaign the next week in the away trip to Huddersfield Town, where he provided the assist for Junior Hoilett's equalising goal.
On 18 March 2014 in away game at Sheffield Wednesday, Yun come in as substitute for Junior Hoilett at half time to cover the left-back position after Richard Dunne had been sent off. QPR lost the game 3–0.[5] In the following game, on 23 March he played full 90 minutes against Middlesbrough and was awarded the Man of the Match.[6] QPR won the game 3–1.[7] He scored his first QPR goal on the 3 May 2014 in a 3–2 win against Barnsley.[8]
Doncaster Rovers (loan)
Yun signed a two-month loan deal with Doncaster Rovers on 25 October 2013.[9]
Charlton Athletic (loan)
On 15 February 2016, Yun signed for Charlton Athletic on loan until the end of season.[10]
Brøndby IF
Signed for Brøndby IF on free transfer on 12 September 2016 a contract for the remainder of the year. On 9 December 2016, Brøndby IF announced, that Yun would leave the club at the start of the new year.[11]
Kashiwa Reysol
On 1 January 2017, he joined J.League side Kashiwa Reysol. Yun made 10 appearances during the 2017 J1 League season, as Kashiwa finished fourth, qualifying for the 2018 AFC Champions League play-off round. The following January, he extended his contract until 2020.[12]
FC Seoul (loan)
On 29 June 2018, he joined K League 1 side FC Seoul on loan for the second half of the season.
Ahead of the 2020 K League 1 season, he joined Busan IPark on loan from Kashiwa Reysol. Yun missed most of the season due to injury, making six appearances in total, as Busan were relegated to K League 2.
Gangwon FC
On 6 January 2021, Yun returned to Gangwon FC, this time on a permanent deal. He scored his first goal for the club in a 3–0 home victory over Daegu FC on 10 April 2021.
International career
Yun played at Under 17 and Under 20 before appearing for the South Korea senior team on 16 October 2009 against Iran in a World Cup qualifier.
In the 2014 FIFA World Cup, Yun appeared in all three of South Korea's games during the group stage. The team finished last in their group with one point.
