2009 K League Championship is postseason championship playoff of 2009 K League. The championship are a series of playoff matches contested by the teams 1st to 6th in the 2009 K League table. All matches are played one leg, except final is played two legs. With 6th playing 3rd and 5th playing 4th, winner of each matches play one match in higher team's homeground. This match's winner gain the next 2010 AFC Champions League spot by the secured 3rd position. The winner of second round playing regular season's 2nd position team in the 2nd team's homeground. The final is played home and away format.
The 2009 K League Championship was won by Jeonbuk for the first time, who defeated Seongnam by the aggregate score of 3-1.