The team announced the move Monday.
Giordano played 15 games for Oakland last season. He led the team with five interceptions and added 66 tackles and one sack.
The 29-year-old Giordano has history with the Raiders new hierarchy. He played one season in Green Bay, where new general manager Reggie McKenzie worked in the personnel department and spent 2010 in New Orleans with Oakland coach Dennis Allen serving as defensive backs coach.
Giordano played his first four seasons with Indianapolis, winning the Super Bowl after the 2006 season. He has eight interceptions in his seven-year career.