The Chiefs' offense started slowly but the Steelers' offense didn't get started until after a blowout had eventually ensued in Kansas City.
The Chiefs scored touchdowns on their final three possessions of the first half and their first three of the second half along the way to a 42-21 victory over the Steelers on Sunday night at GEHA Field at Arrowhead Stadium.
The Steelers exited the playoffs with an overall record of 9-8-1.
The Chiefs moved on to the next round at 13-5.
Kansas City's offensive explosion included a trick-play, 2-yard touchdown pass from tight end Travis Kelce to wide receiver Byron Pringle at the end of a nine-play, 75-yard drive in 4:57.
Kicker Harrison Butker's extra point gave the Chiefs a 42-14 lead with 14:13 left in the fourth quarter.
Quarterback Patrick Mahomes' fifth touchdown pass of the night, a 31-yard strike to wide receiver Tyreek Hill, and Butker's extra point gave the Chiefs a four-touchdown advantage at 35-7 with 9:14 left in the third quarter.
Kansas City took over at the Steelers' 29-yard line after running back Najee Harris' first fumble of the season (forced by linebacker Willie Gary, recovered by defensive end Frank Clark) on what became a two-snap scoring possession.
The Chiefs took command by driving 68 yards on nine plays in 4:47, a march that concluded on a third-and-goal, 1-yard touchdown pass from Mahomes to guard Nick Allegretti, who had reported as an eligible receiver.
Butker's extra point gave the Chiefs a 28-7 lead with 10:13 left in the third.
The Chiefs took a two-score lead via a six-play, 80-yard drive in 39 seconds that ended with a 48-yard touchdown pass from Mahomes to Kelce on third-and-20 from the Steelers' 48 with 22 seconds left in the second quarter.
Butker's extra point upped the Chiefs' lead to 21-7.
The Chiefs took their first lead late in the second.
Big plays highlighted a seven-play, 74-yard drive in 2:43 that ended with a 12-yard touchdown pass from Mahomes to Pringle, a pump-fade to the corner of the end zone that beat cornerback Joe Haden.
A 31-yard catch-and-run connection from Mahomes to Kelce, a 15-yard burst by running back Jerick McKinnon and a 13-yard run by McKinnon helped set the stage for the go-ahead touchdown pass.
Butker's extra point gave the Chiefs a 14-7 lead with 1:55 left in the first half.
Kansas City scored its first touchdown on a 4-yard shovel pass from Mahomes to McKinnon. The eight-play, 76-yard drive in 4:56 included a 23-yard scramble by Mahomes on first-and-15 from the Steelers' 25.
Butker's extra point tied the game at 7-7 with 5:45 remaining before the break.
The Chiefs out-gained the Steelers, 302-44 in the opening 30 minutes and had a 16-2 edge in first downs.
The Steelers opened the scoring with a splash play on defense after a scoreless first quarter.
Outside linebacker T.J. Watt recovered a fumble forced by defensive tackle Cam Heyward and returned it 26 yards for a touchdown with 10:41 left in the second.
Kicker Chris Boswell's extra point gave the Steelers a 7-0 lead.
Watt deflected a pass that was intercepted by inside linebacker Devin Bush on first-and-10 from the Steelers' 22 following a 48-yard punt return by wide receiver Mecole Hardman.
The Steelers scored their first offensive touchdown on a 13-yard touchdown pass from quarterback Ben Roethlisberger to wide receiver Diontae Johnson with 4:10 left in the third.
The drive covered 75 yards on 10 plays in 5:04 and ended on the 35th touchdown pass of Roethlisberger's postseason career, seventh on the NFL's all-time list.
Boswell's extra point drew the Steelers to within 35-14.
Roethlisberger added a 15-yard touchdown pass to wide receiver James Washington with 7:36 left in regulation, his 36th in a playoff game, one behind Drew Brees for No. 6 all-time.
Roethlisberger's 147 yards passing to that point against the Chiefs elevated him to No. 3 on the NFL's career playoff passing yards list at 5,904, ahead of Joe Montana (5,772) and Brett Favre (5,885). Roethlisberger ended up with 5,962 postseason passing yards.
Roethlisberger finished having completed 29 of 44 passes for 215 yards passing, with two touchdowns and no interceptions in the game that ended his 12th trip to the playoffs and, in all likelihood, his 18-year career with the Steelers.
"I'm proud to play with these guys," said Roethlisberger. "God has blessed me with an ability to throw a football and has blessed me to play in the greatest city, in Pittsburgh with the greatest fans and the greatest football team and players. And it has just been truly a blessing and I'm so thankful to Him for the opportunity that He's given me.
"Just a bunch of guys that fought for each other, that fought their butts off and just competed. It wasn't always pretty, but there are a lot of games that we found a way. I'm so proud of this group of men and the way they fight for each other, for the black and gold, for our fans. It's just been an honor to play with them."
The 15-play, 75-yard drive in 6:37 included conversions on fourth-and-1 from the Steelers' 34 (an 8-yard gain by running back Benny Snell) and fourth-and-2 from the Chiefs' 20 (a 15-yard completion from Roethlisberger to Johnson).
Boswell's extra point accounted for the 21-point final margin.
Roethlisberger's final pass found tight end Zach Gentry, who was tackled at the Chiefs' 4.
Wide receiver JuJu Smith-Schuster returned after landing on the Reserve/Injured list and undergoing shoulder surgery following the Steelers' 27-19 win over Denver on Oct. 10.
Smith-Schuster caught five passes for 26 yards.
