The 5-11, 210-pound Anderson has played in 30 games with 18 starts at strong safety in two seasons since being drafted by Green Bay in the third round of the 2002 NFL Draft out of UCLA.
"He is a physical player, a very good tackler and a guy we have had in our sights for some time," Raiders head coach Norv Turner said. "He can help us as we go through the season."
Anderson earned Packers "Defensive Rookie of the Year" honors and was a finalist for "Pepsi NFL Rookie of the Year" in 2002, when he recorded 61 tackles, seven passes defended, two fumble recoveries and three interceptions, two of which he returned for touchdowns. As a rookie, Anderson won the NFL's weekly defensive rookie of the week honors three times.
"I'm excited about joining the Raiders," said Anderson. "I'm very much looking forward to this opportunity."
Anderson started 11 games in 2002 and seven last year, plus both of the Packers' playoff games. He spent the latter part of last season as the starting strong safety.
Anderson has career totals of 139 tackles, 96 of them solo, five interceptions and four fumble recoveries in 30 career games. In three playoff games, he's tallied 18 tackles and one sack.