Desperately needing a win to breathe life back into their NRL season, Dylan Brown and Mitch Moses starred for the Eels as they claimed their biggest scalp of the year.
The result means Penrith will enter the State of Origin period on top of the ladder for the third straight season, claiming first spot off Souths.
Almost everything appeared set up for the Rabbitohs in their first home game at the new Allianz Stadium.
With five First Nations players in their side on Friday night, the Bunnies have not been beaten in Indigenous Round since 2015.
They have also had the wood over the Eels in recent years, winning all six games since 2020 with an average margin of 23.7 points.
And by just after halftime Parramatta were reduced to a two-man bench, with Andrew Davey concussed early and Ryan Matterson suffering a calf injury.
But ultimately, the Eels needed it more to climb from 14th spot on the ladder to within four points of the top eight.
They led the game for all but five minutes in the second half, and were able to claw back the momentum of Cody Walker, Latrell Mitchell and Alex Johnston.
The Eels dominated the middle, Wiremu Greig totalling 200 metres and Junior Paulo 198 to lay the platform for their halves.
Brown in particular was impressive.Â
He laid on a try in the first half when he went to the line from within his own half and offloaded for Matterson before Bailey Simonsson crossed.
He was again influential in Simonsson's second try after the break, putting in a shallow cross-field kick for Clint Gutherson to bat back and help Junior Paulo put the centre over.
Moses also had big moments on return from concussion.
He sent Sean Russell over the for opening try of the match, and later drew in the numbers to put Will Penisni and Bryce Cartwright over on the right edge as well.
The two halves also combined in the second half when Brown charged onto a Moses grubber kick to get the ball down within centimetres of the dead-ball line.
Souths halves, in comparison, couldn't get it done in the key moments.
Walker was electric as he and Mitchell combined for both Johnston's first-half tries, before also sending Campbell Graham over after the break.
But Lachlan Ilias put two kicks out on the full in the second half under immense pressure from the Eels' forwards.
Parramatta scored from each of the next two sets, allowing the Eels to take the lead and then later extend it during the second half.
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