The move comes one year after the Bears signed Porter to a three-year, $12 million deal. He spent the past two seasons in Chicago.
The Bears continue to overhaul their secondary, signing cornerbacks Prince Amukamara and Marcus Cooper during free agency.
Porter, 30, played in 30 games, with 28 starts, over the past two years but battled knee injuries last season. In 2016, he still played in all 16 games and recorded 48 tackles, two interceptions and nine passes defended.
Porter did not start the Bears' season finale in Minnesota because he overslept and missed the team bus to the stadium.
Porter, who was selected by New Orleans in the second round of the 2008 NFL Draft out of Indiana, spent his first seven NFL seasons with the Saints (2008-11), Denver Broncos (2012), Oakland Raiders (2013) and Washington Redskins (2014). He clinched the Saints' Super Bowl XLIV win over the Indianapolis Colts by intercepting a Peyton Manning pass and returning it 74 yards for a touchdown.