Sophomore running back Zach Zwinak added 101 yards and two touchdowns for Penn State (3-2) and the Nittany Lions forced three turnovers and held the Illini (2-3) scoreless for the first 34 minutes.
After starting the season amid turmoil with two losses, Penn State has won three straight.
Linebacker Mike Mauti, one of the most vocal critics last summer of Illinois for its efforts to recruit Penn State players after the child-sex scandal and NCAA sanctions, intercepted Illini quarterback Nathan Scheelhaase twice.
The second came near midfield late in the third quarter as Scheelhaase tried to rally the Illini. Mauti's pick instead set up a 1-yard touchdown run by Zwinak with 14:03 left in the game that sealed the win.
The Nittany Lions must still be wondering how they didn't turn the senior linebacker's first interception into points.
With just seconds left in the half. Illinois was desperately trying to put its first points on the scoreboard, and was in position to do it with a fourth-and-goal from the Penn State 7.
Quarterback Nathan Scheelhaase saw receiver Ryan Lankford crossing the field at the goal line but Mauti stepped in front of the pass, picking it off and charging to his left and the home sideline.
Mauti followed his blockers, running through traffic deep into Illini territory. But he was also running out of gas with Illinois' Miles Osei on his tail.
Osei, the officials ruled after reviewing the play, got just enough of Mauti to force one of his knees to the turf before the linebacker fell across the goal line. But the review also showed one second left on the clock.
Illinois finally found the scoreboard early in the third quarter, but it took a combination of special teams, defense and little offensive sleight of hand to do it.
Illini punter Justin Duvernois pinned the Nittany Lions on their own 1 with a 57-yard punt and Illinois' defense held. After a punt the Illini took over at the Nittany Lion 42.
After moving to the Penn State 22, Illini running back Josh Ferguson took the ball from Scheelhaase and passed deep to wide receiver Spencer Harris in the Nittany Lion end zone to cut the gap to 21-7.
But Illinois struggled to move the ball from that point on.
Scheelhaase finished with 270 passing yards, going 28 of 46. Lankford had seven catches for a game-high 104 yards.
Illinois quite literally handed the Nittany Lions the first points of the game.
Penn State drove to the Illinois 7 and was stopped there. But Bentley was flagged for grazing Ficken's kicking leg, giving Penn State a first down. Zwinak plowed into the end zone from a yard out for a 7-0 lead with 10:41 left in the first quarter.
Penn State added another touchdown four minutes later on a 1-yard run by McGloin to go up 14-0.
The hard feelings between the teams were sometimes clear.
Players exchanged words as they crossed paths on the way to the locker rooms at halftime and had to be separated by officials and staff members from each team.
And Illinois safety Earnest Thomas was ejected from the game after a hard helmet-to-helmet hit on Matt Lehman in the end zone as the tight end caught a second-quarter touchdown. Penn State staff led the groggy Lehman off the field but he returned and finished with five catches for 70 yards.