The two-year starter is now signed through 2012 and is guaranteed $5.2 million over the next two seasons.
"We're very flattered," Williams' agent Albert Elias told The Associated Press. "When you're two years into a contract, these types of extensions aren't normally made.... We're really excited about it." Elias said the Bills contacted him last week to restructure Williams' contract.
The Bills confirmed the new deal, but did not release the terms.
Williams received a roster bonus of $1.75 million and will make a base salary of $700,000 this season, a significant raise over the $445,000 he was scheduled to make under his previous contract. Williams is also due a $1.5 million bonus in March. Williams had two years left on his contract.
Under the new contract he will make a base salary of $12 million over the next five years, not including bonuses.
The Bills' fifth-round pick in the 2006 draft out of Louisiana State has two sacks, both last season, in 32 career games.
The Bills are off until the opening of training camp on July 25.