The AFC has approved criteria for participation in the 2011 and 2012 seasons. The final decision date was set after the Executive Committee meeting in November 2010.
On 30 November 2009, the AFC announced 12 more MA's that were keen to join the ACL, in addition to ten participating national associations. Singapore later withdrew. The full list of candidate associations were as follows:
It was originally announced that the allocation for entry to the 2012 ACL would stay the same as the previous three seasons with the exception of Vietnam, who were disqualifed, and their previous playoff slot was awarded to Qatar. However, following the AFC Executive Committee meeting in November 2011, it was decided that the number of slots for each association to be changed based on evaluation of the AFC Champions League criteria that took place in 2011.
A total of eleven member associations (see below) which participated in the 2011 AFC Champions League was evaluated for participating in the 2012 AFC Champions League.India, which played in the 2011 ACL play-off, was not evaluated and dropped to the AFC Cup. The other member associations which applied but did not meet the criteria for 2011 ACL was not evaluated at all for 2012.
E China was allocated a berth in the qualifying play-off, but Liaoning Whowin, the 2011 Chinese Super League 3rd place, did not enter the competition. Therefore, only four teams entered the East Zone qualifying play-off.
A total of 37 teams participated in the 2012 AFC Champions League.
28 teams (14 in West Asia Zone, 14 in East Asia Zone) directly entered the group stage.
9 teams (5 in West Asia Zone, 4 in East Asia Zone) competed in the qualifying play-off, which was divided into two rounds. The 4 winners (2 in West Asia Zone, 2 in East Asia Zone) qualified for the group stage. Losers of the qualifying play-off final round entered the 2012 AFC Cup group stage. However, losers of the qualifying play-off semi-final round were eliminated from all AFC competitions, a change from previous seasons where they would also enter the AFC Cup.
Group stage direct entrants: West Asia Zone (Groups A–D)
‡Persipura Jayapura were initially disqualified by the AFC from participating but on appeal to the Court of Arbitration for Sport, the CAS ruled on 1 February 2012 that they should be provisionally reinstated to the competition and were entitled to play in the qualifying play-off.
Al-Kuwait (Kuwait), the 2011 AFC Cup runners-up, failed to fulfil the criteria set by AFC to compete in the 2012 AFC Champions League, and thus directly entered the 2012 AFC Cup. Nasaf Qarshi (Uzbekistan), the 2011 AFC Cup winners, already directly qualified for the group stage based on their domestic performance.
The draw for the group stage was held in Kuala Lumpur, Malaysia on 6 December 2011. Clubs from the same country may not be drawn into the same group. The winners and runners-up of each group advanced to the knockout stage.
Brisbane Roar and Beijing Guoan are tied on their head-to-head record (2 pts, 0 GD, 2 GF), overall goal difference and overall goals scored, and so are ranked by their fair play record (Brisbane Roar: 9 YC + 1 RC = 12 pts; Beijing Guoan: 12 YC + 2 RC = 18 pts).
The matchups for the round of 16 were decided based on the results from the group stage. Each tie was played as one match, hosted by the winners of each group (Team 1) against the runners-up of another group (Team 2).
The draw for the quarter-finals, semi-finals, and final was held in Kuala Lumpur, Malaysia on 14 June 2012. It determined the matchups for the quarter-finals and semi-finals as well as the potential host for the final.
The final of the 2012 AFC Champions League was hosted by one of the finalists, decided by a draw. According to the draw on 14 June 2012, the winner of semi-final 2 would host the final. Therefore, Ulsan Hyundai was the home team.