Flowers, 28, made the Pro Bowl for the first time last season, and should help bolster a San Diego pass defense that finished 29th in passing yards allowed per game last season.
Part of the appeal for the Virginia Tech product to sign with the Chargers was the opportunity to play against his old team, the Kansas City Chiefs, twice a season. The Chiefs released Flowers in a cost-cutting move earlier this month.
The one-year deal can reach up to $5 million as $1.5 million comes in the signing bonus, plus a base salary of $1.5 million which is also guaranteed, a source told ESPN's Field Yates.
Flowers can earn $2 million more in incentives. In order to make the full $2 million, he must play at least 92.5 percent of the Chargers' defensive snaps and the team must make the AFC championship game. If he plays at least 78.5 percent of the defensive snaps, he will earn at least $1 million. For context, he played 78.11 percent of the Chiefs' defensive snaps last season while missing 3 games.
At 5-foot-9 and 187 pounds, the cat-quick Flowers fits well in Chargers defensive coordinator John Pagano's system. Flowers can play on the perimeter or inside as a slot defender. Last season for the Chiefs, Flowers played mostly inside, finishing with 68 tackles, a sack and an interception.
Flowers has 17 interceptions -- including three returned for touchdowns -- and 91 pass breakups in his six-year professional career. He joins a roster that currently has Richard Marshall and Shareece Wright penciled in as the team's starting cornerbacks.
This year's first-round selection in the draft for the Chargers, Jason Verrett, also will compete for time with the starters once he's fully healthy. The TCU product is rehabbing from offseason shoulder surgery to repair a torn labrum, but could be ready for full contact at the start of training camp.
The addition of Flowers gives the Chargers added insurance in case it takes longer for Verrett to work himself into the defensive backfield rotation.
The Chargers have a full, 90-man roster, and will have to release a player in order to make room for Flowers. San Diego now has 11 cornerbacks with the addition of Flowers -- Crezdon Butler, Marcus Cromartie, Chris Davis, Greg Ducre, Brandon Ghee, Brandon Jones, Steve Williams, Marshall, Wright and Verrett.