His agency Sports Trust Advisors announced the signing Wednesday. McClain will sign a one-year deal worth $5 million, a league source told ESPN's Ed Werder.
The eighth overall pick in the 2010 draft by the Raiders, McClain found a home with the Cowboys after being acquired in a trade from the Baltimore Ravens on July 1, 2014, when Dallas was seeking a replacement for Sean Lee, who went down with a season-ending knee injury in the first offseason workout of the year.
On the field, McClain has produced. He led the Cowboys in tackles in 2014 despite playing in just 13 games. In addition to the 108 tackles the coaches credited him with, he also had a sack, nine tackles for loss, five quarterback pressures, five pass deflections, a forced fumble and two interceptions.
After he was suspended the first four games in 2015 because of multiple violations of the league's substance abuse policy, McClain started 11 games and finished with 97 tackles, according to the coaches' breakdown, to go along with nine tackles for loss, 10 quarterback pressures, two sacks, one interception and three pass deflections.
He missed last year's offseason program and training camp because of knee surgery, choosing to do his rehab in Alabama instead of at the team's facility. He was cleared for practice just before the regular season -- and his suspension -- began.
McClain, who turns 27 on July 14, retired twice, sitting out the 2013 season after signing with the Ravens. He retired again on April 23, 2014, but was reinstated after his trade to the Cowboys.
While he was out of football in 2013, McClain was arrested for a third time since 2011 in his hometown of Decatur, Alabama, on charges of disorderly conduct and resisting arrest. He was convicted by a judge a year later in a trial held just as training camp with the Cowboys was starting, but the case was dismissed during appeal.
Now that the Cowboys have secured McClain, they are likely to look for pass-rushing help for a defense that needs impact players after Dallas finished last in the NFL in takeaways (11) and turnover margin (minus-22) in 2015.
Troubled defensive end Greg Hardy is unlikely to return after a tumultuous season in Dallas related to his domestic violence case in North Carolina. Second-year end Randy Gregory will miss the first four games on a substance-abuse suspension.
ESPN Cowboys reporter Todd Archer and The Associated Press contributed to this report.