Connor says he's "very excited" about returning to the Panthers, who drafted him in the third round in 2008.
Two people familiar with the deal told the Associated Press that Connor agreed to a one-year contract.
Connor played four seasons for the Panthers before joining the Dallas Cowboys as a free agent in 2012. He played one game this season for the New York Giants before being placed on injured reserve and released.
Connor's best year came in 2011 when he had 75 tackles for the Panthers.