Örebro wanted to shake off the bottom team.
Elfsborg needed victory to get on the top battle train with Malmö as train driver.
The match swung from the start and with just over a quarter played, Per Frick had made it 1-0 and Nahir Besara equalized - both on penalties.
Two minutes later, Rasmus Karjalainen stepped in as a replacement for Jake Larsson - and nodded in a post that meant 2-1 to Örebro.
The post was beaten by Deniz Hümmet, who was loaned out from Elfsborg to Örebro at the end of August and who fixed the home team's penalty.
Wanted free kick
Elfsborg chased the equalizer and Frick thumped the ball into the crossbar, before Rasmus Elm easily put 2-2 just before the break.
The goal was caused by a situation where ÖSK wanted a free kick after an Elfsborg player collided with goalkeeper Oscar Jansson.
Jansson got revenge when he stood in the way of Simon Olsson's right foot twice from close range in the second half.
The jumper hero
The team took turns creating chances in a more balanced event - as incoming Karjalainen would decide in match minute 83.
Besara served him a golden position via a pass along the hill and Karjalainen slammed in the final result 3-2 for Örebro.
ÖSK thus climbs up to ninth place with seven rounds left to play.
Elfsborg has not won since 13 August.