Kim’s international career began in 2009 as a member of the South Korea U-20. He participated in the 2009 FIFA U-20 World Cup, scoring 2 goals in 4 matches. After the U-20 World Cup, he was selected by Hong Myung-Bo, then the head coach of the South Korea U-23 team.

In 2010, Kim dropped out of Hongik University and signed a three-year contract for J1 League side Cerezo Osaka. After he was loaned out to J. League Division 2 side Oita Trinita for the 2010 season, he returned to Cerezo Osaka. During the 2011 season, Kim scored 8 goals. In 2012, while Levir Culpi resigned and Cerezo Osaka appointed Sérgio Soares as the new manager, he remained a key player for the team, scoring 7 goals in 15 matches. When he left the team to participate in the 2012 Summer Olympics, he was the fourth leading goal scorer in J1 League.

On 9 January 2010, Kim made his first international appearance for South Korea in a friendly match against Zambia and participated in the 2010 World Cup later that year. He scored his first and second goals on 12 June 2012, in a World Cup qualifying match against Lebanon.

On 10 July 2012, his agents confirmed that his club Cerezo Osaka, had entered talks with Welsh Championship side Cardiff City over a possible transfer. On 12 July, Cardiff City and Cerezo Osaka agreed to a fee believed to be around £2.5 million. The deal was completed on 27 July, when Kim signed a three-year deal. He made his debut on 18 September in a 2–0 win over Millwall coming on for Craig Noone. Kim’s first start for Cardiff came against Burnley in a 4–0 win at Cardiff City Stadium on 27 October. Kim scored his first goal for Cardiff in their 4–1 victory over Blackburn Rovers on 7 December. His second was the opening goal at Blackpool in a 2–1 victory for Cardiff on 19 January.

On 17 April 2013, Cardiff City won the Championship title and were promoted to the Premier League, making Kim the 12th Premier League player from Korea. He scored his first Premier League goal against Manchester United on 24 November 2013, to secure a late 2–2 home draw with an injury time headed equaliser.

On 24 January 2015, Cardiff City announced Kim’s contract had been terminated by mutual consent.

On 6 February 2015, Wigan Athletic announced that Kim agreed a contract until the end of 2014–15 season. After his contract expired, local rivals Blackburn Rovers tried to sign him, but Kim failed to get a work permit.

At the 2016 FIFA Club World Cup, Kim scored once against America and once against Mamelodi FC.