A try to Wests Tigers centre Chris Lawrence with five minutes remaining has given his side a gutsy 20-16 victory over Cronulla in a pulsating clash at Toyota Stadium.
The Sharks looked like holding on for another tight win when they edged ahead 16-14 with 11 minutes left.
But the Tigers had the final say, Lawrence the first to reach a Mathew Head grubber and get a hand on the ball for a courageous victory in front of a 17,241 fans.
In further good news for the joint venture club, Benji Marshall made a cautious but successful return from a knee injury.
Cronulla had all the ball and territory in the early stages but failed to convert its dominance into points.
Half-back Brett Kimmorley finally got the Sharks going after 17 minutes, throwing a dummy on the 40m line and shrugging off Lawrence's tackle before finding Brett Kearney backing up on the inside for a tremendous try.
Luke Covell's conversion from in front had the home side up 6-0.
But the game slowly changed complexion late in the half, with the Tigers picking up possession and feeding off Cronulla's numerous mistakes.
The visitors were rewarded eight minutes before the break, in-form second-rower Chris Heighington burrowing his way over from dummy half.
Brett Hodgson's conversion struck the upright but the Tigers didn't have to wait long to hit the lead.
From yet another Cronulla mistake, the joint venture side went wide from the scrum through Hodgson.
His well-timed pass sucked in Sharks centre David Simmons, leaving Lawrence a clear 35m passage to the line.
Hodgson's conversion again hit the post but, despite being under the hammer for most of the half, the Tigers had somehow crafted out an 8-6 half-time lead.
Covell levelled things up at 8-all with a penalty seven minutes after the resumption.
But a soft try to Hodgson, who feigned to pass from dummy half and strolled over from close range, put the Tigers back in control 14 minutes into the second half.
With the try-scorer finding his radar with the boot, the conversion had Wests enjoying a 14-8 advantage.
The Sharks needed to score next to stop the game slipping further away and five-eighth Brett Seymour answered their prayers just after the hour.
He did it all himself, running the ball close to the Tigers line before pushing off Corey Payne to score beside the posts.
Covell converted to again have the side all square at 14-all.
He pushed Cronulla further ahead with a 69th minute penalty before Lawrence ensured more heart-break for the Sharks with his second try at the death.
Cronulla 16
Tries: Kearney, Seymour
Conversions: Covell 2
Penalties: Covell 2
Wests Tigers 20
Tries: Lawrence (2), Heighington, Hodgson
Conversions: Hodgson 1
Sportal Player of the Year
3 - Brett Hodgson (Tigers)
2 - Chris Lawrence (Tigers)
1 - Paul Gallen (Sharks)