Charles is the second Chiefs player in the final year of his contract to sign an extension this season. Last month, linebacker Derrick Johnson agreed to a new five-year deal worth as much as $35 million.
Charles acknowledged the signing on his Twitter account.
In signing Johnson, 28, and Charles, 23, the Chiefs are whittling away at their list of key young players in the final season of their contracts. Linebacker Tamba Hali and cornerback Brandon Carr are in the final seasons of the contracts they signed as rookies, Hali in 2006 and Carr in 2008.
Charles turns 24 on December 27th.