The former Kansas City Chiefs great signed with Oakland on Friday, NFL Network's Mike Silver reported. The team later made the announcement official.
The agreement comes a day after Johnson visited his former rival.
Signing the 35-year-old Johnson continues the Raiders' offseason of adding aging veterans. Johnson has clearly lost a step but was reasonably effective in 15 games last season despite rupturing his Achilles tendon late in the 2016 season. Johnson compiled 71 tackles and seven passes defended in 2017.
The veteran should immediately upgrade the coverage ability of the Raiders' second level, a liability of a poor defensive unit last season. Oakland needed a veteran presence in a linebacking corps it did little to upgrade from 2017.
After 13 seasons patrolling the middle of K.C.'s defense, the Chiefs opted not to re-sign the long-time great as the team pivoted toward younger players.
It's possible signing Johnson could shut the door on a return of veteran NaVorro Bowman, whom GM Reggie McKenzie had said he'd hoped to re-sign. The Raiders were also slated to visit with former Texans linebacker Brian Cushing on Sunday, but cancelled the visit, NFL Network's Mike Garafolo reports, according to a source informed of the team's plans.