Branch had already inked his $6.212 million franchise tender, but the sides were interested in an extension to help lower the safety's cap number for the 2012 season.
NFL.com's Steve Wyche reports the deal at $26.6 million with $17.1 million guaranteed over four seasons.
The Raiders on Saturday evening confirmed that the two sides had come to an agreement.
Branch has been one of the few bright spots in Oakland's secondary, recording 100-plus total tackles in each of the past three seasons. He's valued for his play against the run, and ProFootballFocus.com rated Branch as one of the better safeties when facing the league's premier tight ends.
Covering the New England Patriots' Rob Gronkowski in Week 4 last season, Branch held the beast to one catch for 15 yards on four targets. We point this out because Branch did the same against Antonio Gates, shutting out the San Diego Chargers tight end one-on-one, according to PFF.
Defenses are going nowhere if they can't stop these new-age, monster tight ends. Branch isn't a premier safety, but he's an important piece of the puzzle in Oakland.