Cox confirmed the deal to The Associated Press by text message Saturday night.
The NFL Network first reported the deal.
Cox, 28, spent the past two seasons in his second stint with San Francisco, and is coming off his best year. The four-year veteran started 14 games and intercepted five passes while also having 53 tackles.
Coming out of Oklahoma State, the 6-foot Cox played with Denver in 2010. He played two games with Seattle in 2013 before going to San Francisco for nine games.
He helps replace Alterraun Verner, who the Titans lost to Tampa Bay in free agency a year ago.
AP NFL website: www.pro32.ap.org and www.twitter.com/AP-NFL
AP Pro Football Writer Teresa M. Walker contributed to this report from Nashville, Tennessee.