Flacco threw for 262 yards on 22-of-31 passing and didn't commit a turnover. His third TD pass to Boldin -- a 27-yard toss with 9:13 to play in the game -- proved to be the decisive score for the Ravens (2-1) in their home opener.
Boldin ended the day with eight receptions for 142 yards. His three scores matched a career high he had set in 2008 when he played for Arizona.
Peyton Hillis, filling in for injured starting running back Jerome Harrison, carried the ball 22 times for 144 yards and a touchdown.
Hillis also caught seven passes for 36 yards out of the backfield for Cleveland (0-3).
Quarterback Seneca Wallace, starting in place of Jake Delhomme, played well and almost engineered an upset, completing 18-of-24 passes for 141 yards with one touchdown and no turnovers.