Parramatta have spoiled Ivan Cleary's return to Penrith after staving off a late fightback to claim a controversial 20-12 boilover in their NRL opener.
The Panthers threatened to repeat last year's famous round-one comeback when they whittled a 14-point deficit to be within two on Sunday.
But the Eels held firm for an impressive triumph against a side widely tipped to be a title contender.
The win came after Michael Jennings, whose sin-binning late in the contest sparked the Panthers revival, was awarded a dubious first-half try.
It also may have come at a cost, with key prop Nathan Brown suffering a suspected torn pectoral that could rule him out for up to three months.
A resolute Eels defence had kept the home side scoreless for nearly an hour at Panthers Stadium when the game turned on Jennings' sin-binning.
The Eels centre denied a maiden NRL try for Maika Sivo when he knocked Isaah Yeo out with a swinging arm that ended him with him being placed on report.
Wayde Egan jumped over not long after, and the 12,604 crowd roared to life when James Tamou barged over soon after that.
However, Jennings sealed the two points when he took a perfectly-timed pass from debutant Dylan Brown in the closing moments.
Mitchell Moses symbolised the Eels' improved defence by producing two try-saving tackles in the space of a minute.
First, the Eels' chief playmaker stopped Reagan Campbell-Gillard close to the line, before preventing Waqa Blake from cleanly grounding the ball moments later.
There was plenty of anticipation entering the second Cleary era at Penrith, however, the home side couldn't have made a worse start.
Numerous mistakes and penalties deep in their half resulted in the Eels enjoying a 22-4 first half advantage in plays inside the opposition 20-metre zone.
The visitors were also more adventurous with the ball, offloading seven times to one that translated into a two-try lead at the break.
Marata Niukore took advantage of a Blake Ferguson tap-back in the 15th minute, while Jennings was also awarded a controversial try.
The video referee gave the green light despite the Eels centre appearing to have juggled the ball into Panthers fullback Dylan Edwards before spinning over.
Penrith forward Hame Sele may have broken his forearm in his club debut.