A source said the maximum value of the deal is just over $4 million.
McClain flew in for a visit to Atlanta on Thursday night and watched the team conduct its rookie minicamp Friday. He is expected to step into the defensive rotation and compete for a starting role at the 3 technique alongside nose tackle Grady Jarrett.
The 6-foot-2, 302-pound McClain, nicknamed the "Dancing Bear'' because of his size and quickness, considered a return to the Dallas Cowboys before agreeing to terms with the Falcons. He also considered the San Francisco 49ers, Philadelphia Eagles and Miami Dolphins.
The Falcons had a void at defensive tackle when Dontari Poe opted to sign with the Carolina Panthers in free agency. McClain, a 2011 third-round draft pick of Carolina out of South Florida, has played for the Panthers, New England Patriots, Houston Texans, Cowboys and Washington Redskins over seven seasons. His career numbers include 110 combined tackles, 6.5 sacks and 3 forced fumbles.
McClain was released by the Redskins in April after signing a four-year, $21 million contract with the team in 2017. He was due to make about $3.25 million in 2018 prior to his release.
The Falcons view McClain as an ideal scheme fit with his ability to get upfield and use his quickness. He can stop the run and has pass-rush ability, something Cowboys defensive coordinator Rod Marinelli noted when McClain came out of college.
The Falcons also added another South Florida product in rookie defensive tackle Deadrin Senat, also a third-round pick. Senat is expected to compete behind Jarrett.
Overall, coach Dan Quinn has high expectations for the defensive line, with Vic Beasley Jr. and Takk McKinley rushing off the edges and Jarrett leading the push on the interior. McClain reunites with close friend Jack Crawford, his former teammate and defensive line partner in Dallas.