Nebraska used a late 14-4 run to take a 70-65 lead with just less than three minutes left. Three-pointers from Matt Gatens and Eric May brought the Hawkeyes within two, but Toney McCray hit two free throws with 27 seconds left and Iowa couldn't answer.
Zach McCabe matched a career high with 20 points for the Hawkeyes (11-10, 3-5), who led by as many as 11 points in the first half.
This was the first meeting in 36 years between the border-state schools, who will now see each other at least once a season.
Iowa will always remember the reunion as the one it let get away.
McCabe, who'd been brilliant all night, picked up his fourth foul with 5:29 left. Nebraska's Brandon Ubel hit two free throws that tied the game at 61, and Richardson hit a crucial three-pointer from the elbow to give the Huskers a 66-63 lead with 4:34 remaining.
Iowa had its chances to tie the game once again, but the Hawkeyes couldn't convert them.
Marble scored 15 points for the Hawkeyes and Gatens had 12.
Nebraska got off to a strong start, hitting nine of its first 12 shots. Yet the Huskers still found themselves down 25-19 midway through the first half.
McCabe, who'd scored in double figures just four times in Iowa's first 16 games, crossed that mark for the third straight game in just 13 minutes. McCabe then followed a layup with a block on McCray and Bryce Cartwright's long jumper to put the Hawkeyes up 31-20.
Faced with their first crucial moment of the night, the Huskers responded with an 8-0 run and went into the break trailing 38-31. Nebraska opened the second half on a 10-1 run to take a brief 41-40 lead.
May helped rally the Hawkeyes with a jarring block on Spencer and seldom-used reserve Devon Archie stunned the crowd by spinning out of traffic in the lane for a monster dunk to put Iowa up 50-43 midway through the final half.
From there, the Hawkeyes seemed poised to methodically put the Huskers behind them. However, they never did, allowing Nebraska to inch back into the game and ultimately take it over down the stretch.