Born in Chuja Islands, an archipelago of Jeju City, Ji began his football career at Gwangyang Jecheol High School.

[3][4] After a brief spell in Reading Academy, Ji moved back to his home country to rejoin Jeonnam Dragons' youth team, where he started his career.

[5] Ji scored 13 goals during 29 appearances in his first professional season including a hat-trick against Gyeongnam in the 2010 Korean FA Cup.

[9] In June 2011, Ji agreed a deal to join Sunderland of the English Premier League as a summer transfer after impressing manager Steve Bruce with his performance in the 2011 Asian Cup, in which he scored four goals and provided two assists in six games.

[14] Ji made his league debut for Sunderland on 13 August 2011 coming on for Asamoah Gyan in the 66th minute against Liverpool.

[15] Ji scored his first Premier League goal in the 90th minute against Chelsea from a Nicklas Bendtner assist on 10 September 2011, to which Sunderland lost 2–1.

[21]Ahead of the 2012–13 season, Ji was told by Manager O’Neill that he needs to develop in the Premier League physically if he is fully deliver on his potential.

[27][28] Although he went on to make the total of seven appearances by the time of his departure, it was revealed that Sunderland failed gain international clearance from the German Football Association, resulting a fine by the Premier League.

[38][39] The club remained interested in signing Ji at the end of the season on a permanent basis, but failed to reach the deadline of purchase option.

[46][47] Ji signed a four-year contract with Borussia Dortmund on 1 July 2014 after finishing his loan spell with Augsburg.

[49][50] Prior his move to Augsburg, Ji found the six months spell at with injuries and playing in the reserve side, as "difficult" there.

[51] On 22 December 2014, after failing to appear competitively for Borussia Dortmund, Ji signed a three-and-a-half-year contract with FC Augsburg, until 30 June 2018.

[58][59] As the 2016–17 season progressed, Ji began playing into a forward role following the absence of Alfreð Finnbogason and Raúl Bobadilla but struggled to score under the new position.

On 1 March 2019, Ji scored twice against his former club Borussia Dortmund and led Augsburg to a stunning 2–1 upset over the league leaders.

[62] After a long spell in Augsburg, Ji moved to Mainz 05 and Eintracht Braunschweig,[63][64] but wasn't impressive in both clubs.

[74] During the tournament, Ji scored four goals in six games, catching Sunderland manager Steve Bruce's eye.