With his Coventry contract about to expire, King was reported to have verbally agreed a new deal with the club.
However, on 10 June 2011, he agreed a three-year contract with Birmingham City, citing the opportunity to play in the Europa League as a major factor in his decision.
The free transfer, under the Bosman ruling, was formally completed on 1 July.
Coventry's chairman and manager felt "betrayed" by the player's actions.

He suffered knee ligament damage in pre-season training which delayed his Birmingham debut until 11 September, when he played the last half-hour of a 3–0 home win over Millwall.
King scored his first goal in European competition on his first start for Birmingham, in the 3–1 home defeat to Braga in the Europa League group stage, and his first League goal for the club on 16 October, a penalty to open the scoring in a 2–0 win against Leicester City.
King finished the season with 18 goals and 12 assists as Birmingham reached the play-off semi-final.

King scored the first senior hat-trick of his career to secure a draw after Birmingham were 3–0 down after 19 minutes away to Millwall in October 2012.
This was the start of a scoring run of nine goals in as many games, finishing with Birmingham's 3–2 defeat of third-placed Middlesbrough in December, in which King was fouled for and converted a penalty just before half-time to level the scores, and ran onto a through ball by Peter Løvenkrands to score the late winner with what the Birmingham Mail described as a "clinical finish".
Although put up for sale in January, a bid from Shanghai Shenhua was rejected in February.
However, in March, his season was brought to a premature close due to a long-term knee injury deteriorated, requiring an operation.
On 28 August 2013, it was announced that Marlon King would be leaving Birmingham, after his contract was terminated by mutual consent in order to reduce the club's wage bill.
With his Coventry contract about to expire, King was reported to have verbally agreed a new deal with the club. However, on 10 June 2011, he agreed a three-year contract with Birmingham City, citing the opportunity to play in the Europa League as a major factor in his decision. The free transfer, under the Bosman ruling, was formally completed on 1 July. Coventry's chairman and manager felt "betrayed" by the player's actions.
He suffered knee ligament damage in pre-season training which delayed his Birmingham debut until 11 September, when he played the last half-hour of a 3–0 home win over Millwall. King scored his first goal in European competition on his first start for Birmingham, in the 3–1 home defeat to Braga in the Europa League group stage, and his first League goal for the club on 16 October, a penalty to open the scoring in a 2–0 win against Leicester City. King finished the season with 18 goals and 12 assists as Birmingham reached the play-off semi-final.
King scored the first senior hat-trick of his career to secure a draw after Birmingham were 3–0 down after 19 minutes away to Millwall in October 2012. This was the start of a scoring run of nine goals in as many games, finishing with Birmingham's 3–2 defeat of third-placed Middlesbrough in December, in which King was fouled for and converted a penalty just before half-time to level the scores, and ran onto a through ball by Peter Løvenkrands to score the late winner with what the Birmingham Mail described as a "clinical finish". Although put up for sale in January, a bid from Shanghai Shenhua was rejected in February. However, in March, his season was brought to a premature close due to a long-term knee injury deteriorated, requiring an operation. On 28 August 2013, it was announced that Marlon King would be leaving Birmingham, after his contract was terminated by mutual consent in order to reduce the club's wage bill.
Marlon King