His agent, David Canter, tweeted out a picture of McCain signing his contract.
A source told ESPN.com's James Walker that McCain received a two-year deal worth $5.5 million.
McCain, 28, resuscitated his career after signing a one-year contract for the veteran minimum last March. He opened the season as the Steelers' No. 4 cornerback but the 5-foot-9, 187-pounder ended it as a starter because of injuries and ineffectiveness at the position.
McCain tied William Gay for the team lead with three interceptions despite starting only eight regular-season games.
His 22-yard interception return for a touchdown helped the Steelers stave off an upset bid in a 17-9 win at Jacksonville in early October. Besides his three interceptions, McCain recorded 24 tackles and defended five passes while also recovering a fumble in 2014.
McCain spent his first five seasons in Houston but he fell out of favor with the Texans and they released him after the 2013 season.
McCain has seven interceptions in six NFL seasons.
ESPN.com Steelers reporter Scott Brown contributed to this report.