Flacco completed 27-of-36 passes while Torrey Smith had eight receptions for 103 yards. Tyron Taylor relieved Flacco and hit 7-of-9 throws for 139 more yards.
Bobby Rainey, LaQuan Williams, Tommy Streeter and Anquan Boldin each had a touchdown catch. Baltimore scored five second-half touchdowns while improving its exhibition record to 2-1.
Blaine Gabbert had 117 passing yards for Jacksonville (2-1).
Jacksonville's first touchdown did not come until the fourth quarter and was produced when Antonio Dennard returned an interception 45 yards for a score.