Baltimore moved 52 yards in 13 plays and 5:31, but stalled at the Steelers' 16 and had to settle for Tucker's 34-yard field goal with 9:21 remaining the third quarter.
Joe Flacco went 5-for-8 for 42 yards on the possession, but didn't complete his last two attempts. He is up to 160 yards.
Now it's the defense's turn to see if it can continue to lock down Ben Roethlisberger and the Steelers offense.
Update: And the Steelers are on the board.
Pittsburgh drove 80 yards in seven plays and 2:58 to cut the Ravens' lead to 13-7 on Roethlisberger's 8-yard touchdown pass to Emmanuel Sanders. The big play on the drive was a 43-yard run by Le'Veon Bell that gave the Steelers first-and-goal at the 8.
Can the Ravens respond?
Update II: Yes, they can. Jacoby Jones returned the ensuing kickoff 73 yards to the Pittsburgh 27.
Right away, Flacco connected with Torrey Smith for a 16-yard pass to get the Ravens down to the 11. Baltimore gained just six more yards and then a 15-yard unsportsmanlike penalty on Ray Rice set the team back to the 20.
But that didn't matter to Tucker, who hit a 38-yard field goal to split the uprights for the third time tonight, this time giving the Ravens a 16-7 lead with 3:49 to go in the third quarter.
On Jones' kickoff, replays showed Steelers coach Mike Tomlin with his back to the play and one foot on the field. He had to jump out of the way, perhaps causing Jones to cut inside and slow up, allowing the last man in coverage to tackle him. Should come up after the game...
Update III: Tucker's fourth field goal of the day, a 45-yarder, has upped the Ravens' advantage to 19-7 with 13:59 to go.
Tucker now has eight field goals over his last two games and has made 26 straight tries. That capped a seven-play, 37-yard drive that was keyed by a 34-yard pass to Jones.
Update IV: Le'Veon Bell's 1-yard touchdown run with 9:32 remaining has cut the Ravens' lead to 19-14.
It was just the second rushing touchdown allowed by Baltimore in 12 games this season.
The Steelers drove 60 yards in 10 plays, eating 4:27 off the clock. The Ravens helped the possession along with back-to-back defensive holding penalties on cornerbacks Lardarius Webb and Corey Graham.
A 19-yard pass to Antonio Brown gave Pittsburgh first-and-goal at the 8.
So this should be a fascinating finish in Baltimore now that it's a one-score game.
Update V: Tucker has tied a Ravens team record with his fifth field goal of the game, a 48-yarder that gave Baltimore a 22-14 lead with 5:37 remaining.
That should give the Ravens a little bit more comfort now that the Steelers need a touchdown and a two-point conversion to tie. But this is another contest where Baltimore seemed in control, but couldn't put the opponent away.
Let's see if it comes back to bite the Ravens. If they hold on, it would be a huge win toward the playoff push. If they lose, they could need plenty of help to get there for a sixth straight season.
Update VI: What a strange series of events.
The Steelers had two touchdown calls in three plays overturned with just over a minute remaining. One was reversed when Heath Miller's knee was down a yard short of the goal line. The second was overturned when Bell's helmet got knocked off before he got in the end zone, rendering the play dead. Bell was knocked out on the play and left the game.
The Steelers finally scored on a 1-yard touchdown pass to Jerricho Cotchery. But a pass to Sanders on the would-be tying two-point conversion fell incomplete. The ensuing onside kick was touched by Pittsburgh before traveling 10 yards, giving the Ravens the ball.
A couple of kneel-downs later, and the Ravens had won 22-20. It marks the fifth straight meeting between the teams that was decided by three points or fewer. Baltimore won its third in four games to improve to 6-6 and now is in solid control of its postseason fate.