Conley, 26, started 3-4 games in his four seasons with all the Kansas City Chiefs since he arrived as a third-round selection (76th overall) by Georgia at 2015.
In his four seasons, Conley has caught 104 passes for 1,238 yards and six touchdowns.
Conley has been limited to five matches in 2017, when his season ended prematurely as a result of a ruptured Achilles tendon.
In addition to Conley, the Jags also announced that they have signed former Cincinnati Bengals offensive lineman Cedric Ogbuehi. A former first-round selection of the Bengals, the 26-year-old Ogbuehi spent last season as a healthy scratch for a Cincinnati team that ended the season 6-10.
The Jags didn’t reveal contract provisions for Ogbuehi or Conley.
ESPN’s Adam Teicher contributed to the record.