No financial terms were disclosed, but ESPN.com’s Adam Schefter reports that the Chargers will sign Johnson to a three-year deal.
Johnson played last season with the San Francisco 49ers, catching 35 passes for 435 yards and three touchdowns in 13 games.
Johnson was acquired by San Francisco from the Buffalo Bills in exchange for a fourth-round pick in May 2014. He spent his first NFL six seasons with Buffalo.
Johnson, 28, was scheduled make $5.5 million and $5.85 million in the final two years of his deal with the 49ers before being released.
In seven NFL seasons, Johnson has 4,267 receiving yards and 31 touchdowns.
- Scooby Axson