The team has not announced any official signing.
McClellan, 29, is one of the team's anchors on special teams and has led the unit in tackles in three of the past five seasons. He was tied for second in special teams tackles last year with six, trailing only safety Brynden Trawick.
Last year's special teams group was viewed as the best in the league, and the Ravens have reportedly taken an early step to stay on top. McClellan was a pending unrestricted free agent.
An undrafted rookie gem in 2011, McClellan is now one of the longest-tenured players with the team and a favorite of the coaching staff.
Not only is he very valuable on special teams, but he has the experience and versatility to help on special teams. Due to Terrell Suggs' first torn Achilles in 2012, McClellan started 11 games and made 49 tackles and one sack during that Super Bowl season.
McClellan can fill in at inside and outside linebacker if needed while providing consistently strong play and leadership to the younger players on special teams.
The Ravens have 10 other unrestricted free agents. The market opens on March 9.