Quarterback Ben Roethlisberger threw a six-yard touchdown pass to game MVP Santonio Holmes with 35 seconds remaining in the game to cap off a 78-yard drive that gave the Steelers their second Super Bowl victory in the past four seasons.
It marked the sixth come-from-behind victory for the Steelers this season. The previous five came during the regular season, when the team went 12-4.
"Oh my God, I don't know how to explain it," said Steelers All-Pro strong safety Troy Polamalu. "You are seconds away from crying in the locker room. That's how amazing this game is."
The Cardinals, making their first Super Bowl appearance, erased a 20-7 Pittsburgh lead by recording a safety and getting a pair of touchdown passes from Kurt Warner to former Pitt star Larry Fitzgerald, the second of which was a 64-yard catch-and-run that lifted the Cardinals to their first lead of the game, 23-20 with 2:37 remaining.
But Roethlisberger and Holmes, who caught nine passes for 131 yards, connected four times in the game's closing moments, the last of which was the six-yard scoring reception.
Holmes somehow caught the ball in the back of the end zone while keeping both feet down in bounds to give the Steelers the lead back with 35 seconds remaining.
"This has been our story all year long," said Steelers second-year head coach Mike Tomlin while accepting the Lombardi Trophy, which is awarded to Super Bowl winners.
"Steelers football is 60 minutes. It's never going to be pretty."
At 36-years-old, Tomlin is the youngest coach to lead a team to a Super Bowl victory.
Linebacker James Harrison, the NFL's Defensive Player of the Year, showed the world why he earned that honor this season, returning a Warner interception 100 yards on the final play of the first half to record the longest play from scrimmage in Super Bowl history.
The Steelers were making their AFC-best seventh Super Bowl appearance and now own a 6-1 record in the Super Bowl. Dallas and San Francisco, both of the NFC, have won five Super Bowls each, while the Cowboys lead all teams with eight appearances in the NFL's championship game.