Tommy Armstrong Jr. had four TD passes for the Cornhuskers (9-3, 5-3 Big Ten), who trailed by as many as 17 points before storming back in the second half.
Nebraska tied the school record for the largest road comeback.
Jordan Canzeri caught a 5-yard touchdown pass with 1:49 left in regulation to put Iowa ahead 31-28. But Drew Brown's 20-yard field goal with 8 seconds left forced overtime.
Jake Rudock had 230 yards and two TD passes for Iowa (7-5, 4-4). The Hawkeyes closed the regular season with back-to-back home losses.
Iowa seemed poised to blow out the Huskers early in the second half, jumping ahead 24-7.
It reality, the game was just getting interesting.
Nebraska responded behind Armstrong, who brought the Huskers back within 24-21 on a 34-yard TD pass to Allen and a 32-yarder to Bell early in the fourth quarter.
Pierson-El had been stopped by Iowa punter Dillon Kidd on his previous return. But he blew past Kidd and the rest of the Hawkeyes to give Nebraska the improbable lead with three TDs in less than 5 minutes.vRudock answered right back though, finding Canzeri alone in the flat for the touchdown. Armstrong wasn't done either, finding Brandon Reilly for a crucial 35-yard completion to set up the game-tying kick.
Marshall Koehn hit a 25-yard field goal in overtime, briefly giving Iowa a 34-31 lead.
Bell's catch was reviewed, but the call on the field was upheld.
Ameer Abdullah had 106 yards rushing and Bell caught two TD passes for Nebraska.
The Hawkeyes dominated the first half, and John Lowdermilk took an interception back 17 yards for a touchdown. But they only led 10-7, largely because of four turnovers.
But Rudock caught Nebraska in a cornerback blitz early in the third quarter and hit Tevaun Smith, who raced 37 yards to put the Hawkeyes up 17-7.
Nebraska Punter Sam Foltz then dropped a snap. He recovered in time to get the punt off, but it ricocheted off lineman Zach Hannon's back. Drew Ott happily scooped up the loose ball, giving Iowa a 24-7 point lead with 8:45 left in the third quarter.
But the Hawkeyes couldn't hold the lead. They wound up finishing fourth in the Big Ten West, a division many thought it could win this season.
Mark Weisman had 82 yards rushing for Iowa.