The deal will pay him $26 million, including $14.625 million guaranteed, according to multiple reports.
The Bills tweeted news of the contract Wednesday:
- Buffalo Bills (@buffalobills) March 5, 2014
While the move comes two days after the Bills opted not to assign the franchise tag to fellow safety Jairus Byrd, CEO Russ Brandon said the two decisions are not related.
"This is completely independent from any other negotiations we have going on," Brandon told reporters Wednesday.
Williams, 23, was entering the final season of his rookie contract. The former second-round pick struggled in his first two seasons as a cornerback before converting to safety last season. In 14 games, he made 82 tackles and had four interceptions.
"Aaron Williams is a versatile player who has grown into a key playmaker for our defense in recent years," general manager Doug Whaley said in a statement. "Aaron is the type of young, core player we targeted early in the process to retain for years to come and this will be our philosophy moving forward."