He thanked the owners of the Chiefs and Chargers in an Instagram post and wrote that he's ready "for this next chapter in my life."
Flowers, who turned 31 in February, played the past three seasons with the Chargers but was placed on injured reserve in December 2016 after suffering a concussion in Week 10 against the Dolphins. In six games (all starts) last season, he finished with one interception and five passes defensed.
Flowers started 30 of the 31 games he appeared in with the Chargers, but was released by the team on March 7, freeing up $7 million in cap space.
Flowers had a tryout with the Arizona Cardinals recently, but the team decided to sign cornerback Tramon Williams instead.
He spent the first six seasons of his career with the Chiefs and was selected to his only Pro Bowl in 2013. He had 17 interceptions and 92 passes defensed in his time in Kansas City.