Roethlisberger threw a short touchdown pass to Weslye Saunders in the first half, and the Steelers took advantage of four turnovers by Chiefs quarterback Tyler Palker in a 13-9 victory that allowed them to keep pace with Baltimore atop their loaded division.
Roethlisberger was 21 of 31 for 193 yards and an interception for the Steelers (8-3), whose defense lost All-Pro safety Troy Polamalu to a head injury in the first quarter yet still kept the bumbling Chiefs (4-7) from scoring a touchdown.
Kansas City hasn't reached the end zone since the third quarter against Denver three weeks ago, a span of 45 offensive drives -- including the final one Sunday night.
The Chiefs marched across midfield to the Pittsburgh 37 when Palko dropped back to pass. He was looking for Dwayne Bowe but threw it high and behind him, and Keenan Lewis hauled in the interception with 29 seconds left to seal the outcome.
He fared little better than he did last week against New England, when he tossed three picks in his first NFL start. Palko finished 18 of 28 for 167 yards in what was likely his last chance.
The Chiefs claimed former Broncos quarterback Kyle Orton off waivers on Wednesday with the intention of having him compete with Palko for the starting job. Orton didn't arrive in town until Friday, though, and he was inactive Sunday night after participating in only one practice.
Kansas City led 3-0 in the second quarter when Palko's first interception, which Taylor returned to the Chiefs 8, resulted in a 21-yard field goal by the Steelers' Shaun Suisham.
The second pick was returned by Mundy, who had taken over at safety for Polamalu, to the Kansas City 24. The defense appeared to hold Pittsburgh when Tamba Hali sacked Roethlisberger on third-and-7, but safety Jon McGraw was called for defensive holding to give the Steelers a first down.
Three plays later, Roethlisberger found Saunders in the back of the end zone.
Ryan Succop added a 49-yard field goal later in the second quarter for Kansas City, his second of the game, but Suisham answered with his own 49-yarder on the final play of the first half.
Succop added a 40-yard field goal with 6:11 left in the fourth quarter.
Polamalu left the game in the first quarter when he tackled 290-pound Chiefs offensive tackle Steve Maneri, who had caught a pass in the flat after lining up in the backfield.
The reigning Defensive Player of the Year's head hit Maneri's knee and he crumpled to the turf, where he lay while trainers came out to check on him. Polamalu was a bit wobbly when he stood up and the team said he was questionable to return with a "blow to the head."
Steelers center Maurkice Pouncey also left in the first half with an illness.
Roethlisberger showed little evidence of the broken thumb that caused him to be somewhat limited in practice, hitting 10 different receivers. He got some help from Rashard Mendenhall, who ran for 57 yards, and a defense that kept giving the Pittsburgh offense prime field position.
The Steelers squandered a promising opportunity in the first quarter, driving inside the Chiefs 10-yard line. But backup running back Mewelde Moore had the ball poked out by Chiefs linebacker Tamba Hali and it was recovered by Javier Arenas in the end zone for a touchback.
Kansas City gave the ball right back when Palko fumbled the snap moments later.
Pittsburgh also had a decent drive end midway through the scoreless third when Roethlisberger underthrew Antonio Brown down the sideline. Kansas City safety Travis Daniels swooped in to make the interception, but the Chiefs' bumbling offense couldn't capitalize.
That wound up being the story of the game.