Ravens open up 34-13 lead after 3 quarters
Ed Reed also scored on an interception return for the seventh time in his career.
The winner of the season-opening matchup between divisional foes gets first place in the AFC North.
Andy Dalton was 4 for 5 for 59 yards on the opening drive of the second half, and his third-down keeper moved the ball to the Ravens' 1-yard line. But the Bengals had to settle for a 19-yard field goal by Mike Nugent, trimming Baltimore's lead to 17-13.
Flacco then took the Ravens 89 yards on nine plays, floating a 10-yard touchdown pass to tight end Dennis Pitta for a 24-13 lead. Pitta backpedaled and outleaped cornerback Leon Hall to snag Flacco's timing-play throw.
On the next series, Ravens coach John Harbaugh successfully challenged a 20-yard completion from Dalton to Andrew Hawkins on third down, and the play was changed to a 6-yard completion because Ray Lewis touched the receiver when his knee was ruled down. Cincinnati was forced to punt and the Ravens took a 27-13 lead on Justin Tucker's 40-yard field goal with 1:13 left in the third quarter.
Reed intercepted a tipped pass on the ensuing possession, returning it 34 yards for a 34-13 lead. Reed has the NFL record for career interception yards with 1,497, breaking the old mark of 1,483 by Hall of Famer Rod Woodson.
Flacco went 12 for 15 in the first half to stake the Ravens to a 17-10 halftime lead.
After Nugent's 34-yard field goal 8 seconds into the second quarter cut Baltimore's lead to 10-3, the Ravens responded by moving 82 yards in five plays and going up 17-3 on Flacco's touchdown pass to Anquan Boldin.
Late in the half, Dalton drove the Bengals to the Baltimore 6-yard line, and on fourth-and-1, BenJarvus Green-Ellis bounced over the goal line for a touchdown.
The Ravens scored on their opening drive, capped by a 46-yard field goal by Tucker, the rookie who wrested the job from incumbent Billy Cundiff in training camp. Flacco's 52-yard pass down the middle to Torrey Smith on Baltimore's first offensive play of the season set up the kick.
After a three-and-out by the Bengals, Flacco moved the Ravens 63 yards in 12 plays, often employing the no-huddle offense. Rice capped the scoring drive with the 7-yard scamper with 6:03 remaining in the opening quarter.
Flacco was 6 for 7 for 49 yards on the march, finding Jacoby Jones for 16 yards on a third-and-15 and converting a fourth-and-1 with a 1-yard toss to Rice.
Before the game, a moment of silence was observed for former Ravens owner Art Modell, who died at 87 on Thursday. Baltimore players wore a decal honoring Modell on their helmets and T-shirts beneath their jerseys bearing the former owner's photograph.