Seongnam FC Kim joined the youth academy of
Seongnam FC and worked his way up their youth categories. In doing so, he became the club's first ever semi-pro player, as well as their youngest registered player in the league that season. He made 19 appearances in his debut season with Seongnam, earning interest from clubs abroad.
Brentford On 26 June 2023, Kim joined
Premier League club
Brentford for an undisclosed fee, signing a four-year contract with the club, with an option for an additional year, and being assigned to the
B team. During a season at the B team, he was on the list of senior squad in eight Premier League matches, but did not make his senior debut. becoming the first-ever Korean centre-back to be affiliated to a Premier League club. He made his Premier League debut on 27 December, coming on as a 76th minute substitute for
Ben Mee in a match against
Brighton & Hove Albion.
Loan to 1. FC Kaiserslautern On 22 July 2025, Kim was loaned by
2. Bundesliga club
1. FC Kaiserslautern, moving to Germany. He could qualify as a
homegrown player if he stayed in England for one more season, but he chose immediate experience on the field after manager
Thomas Frank, who had asked him to stay at the club, left for
Tottenham Hotspur. However, Kim injured his thigh in a league match against
Fortuna Düsseldorf on 2 November, and suffered a relapse two months after starting rehabilitation. ==International career==