The team announced it was also placing CB Jason Verrett on injured reserve.
Verrett, 28, was taken with the No. 25 overall pick back in 2014 by the Chargers. He finished his four-year rookie contract and played out 2018 under the fifth-year option for $8,526,000.
Verrett has landed on injured reserve for last three consecutive years. He missed all of last season due to a ruptured Achilles. He signed with San Francisco this offseason on a one-year deal.
In 2017, Verrett appeared in one game and recorded one tackle and no interceptions.
Johnson, 27, is a former fourth-round pick of the 49ers back in 2014. He played out the final year of his four-year, $2,620,544 contract with the 49ers before signing on with the Seahawks in 2018.
After brief stints with the Bills and Cardinals in 2018, Johnson signed on with the Chiefs this offseason. Kansas City released him in May and Johnson returned to the 49ers, only to be let go during final roster cuts.
The Chargers signed him to their active roster earlier this month only to release him when Melvin Gordon returned, making his stint in Los Angeles short-lived.
In 2017, Johnson appeared in all 16 games for the 49ers and recorded 77 tackles, one interception returned for a touchdown and seven pass defenses.