Tucker's kick was set up when Corey Graham picked off a Peyton Manning pass at the Denver 45-yard line. Two plays later, the Ravens kicker drilled a field goal to boost Baltimore into the AFC Championship Game.
There they will play the winner of Sunday's match-up between New England and Houston.
Flacco finished 18-of-34 through the air for 331 yards and three scoring strikes with no interceptions, while Torrey Smith ended with three catches for 98 yards and a pair of scores in the victory.
Ray Rice rambled for 131 yards on 30 carries with a touchdown for Baltimore.
Manning completed 28-of-43 passes for 230 yards and a trio of TD passes but lost a key fumble for the Broncos.
Eric Decker and Joel Dreessen each made six grabs for a combined 130 yards in the loss.