Barner ran for 129 yards and two touchdowns and caught five passes for 42 yards in 13 games for the Philadelphia Eagles last season.
The Chargers will have a healthy Melvin Gordon in 2017 after a knee injury knocked him out of the team's final three games last year.
Barner will likely compete with Kenneth Farrow to win the backup running back job behind Gordon. In addition, Los Angeles will have to replace the production it lost when Danny Woodhead signed with the Baltimore Ravens.
Barner had a nice college career, finishing sixth in FBS in rushing yards (1,767) as a senior in 2012, but the 27-year-old struggled to carve out a meaningful role in Philadelphia after the Eagles acquired him from the Carolina Panthers.
Barner averaged 4.6 yards a carry in 24 games for the Eagles, so he may only need the right opportunity to become a useful piece of the Chargers offense.
Having averaged 30.8 yards on nine kick returns for Philadelphia in 2016, he could also help Los Angeles in special teams.