The Steelers scored with 63 seconds to play after two previous apparent touchdowns were negated by video review, but Pittsburgh's attempt to tie it with two-point conversion failed when Emmanuel Sanders could not hold onto a pass thrown by Ben Roethlisberger.
Pittsburgh's ensuing onside kick failed to go the needed 10 yards, giving the ball to Baltimore.
The Ravens ran out the clock to even their record at 6-6, moving them within 1 1/2 games of Cincinnati for the lead in the AFC North. Cincinnati will meet San Diego on Sunday. Pittsburgh fell to 5-7.
Baltimore never trailed, taking the lead in the opening period on a 7-yard throw from Joe Flacco to Torrey Smith.
Tucker then kicked field goals of 43, 34, 38, 45 and 48 yards. The last of those kicks came with 5:37 to play and put the Ravens in front by eight points.
Pittsburgh then marched 79 yards to a touchdown, but it came only after a series of unusual plays on the goal line.
Heath Miller appeared to have scored on a 20-yard catch, but it was eventually ruled he was down at the 1-yard line.
Two plays later Le'Veon Bell bulled into the end zone, but his helmet was knocked off an instant before he crossed the goal line. NFL rules say a play is whistled dead when a ball carrier's helmet comes off, so the touchdown was again waived off.
Bell had to leave the game with a possible concussion, but Pittsburgh eventually scored on Roethlisberger's 1-yard throw to Jerricho Cotchery. All of that work went to waste, however, when the Steelers could not convert the conversion try.
Flacco completed 24-of-35 for 251 yards without an interception.