Andrew Fifita helped the Sharks fight back in the second half to beat North Queensland 18-14.
The Cronulla prop was key to his side's comeback from a 14-point interval deficit to win at home for just the second time this year.
The reigning premiers ran in three unanswered tries in the second stanza to join the Storm at the top of the NRL ladder.
The Cowboys did well in the absence of star playmaker Johnathan Thurston and looked to be well in command when they scored two tries in the space of six minutes just before the break.
Jason Taumalolo was outstanding for the visitors with over 200 metres and a stack of tackle breaks in a losing effort.
Fifita and James Maloney turned the game on its head, Maloney bursting into life 10 minutes into the second half when he dummied and stepped his way through the line to bring Cronulla to within eight points.
Fifita then skittled several would-be defenders before offloading to a flying Chad Townsend to bring the hosts to within two.
A big shot by Luke Lewis on Lachlan Coote forced a turnover on halfway, and from the ensuing set Valentine Holmes got on the outside of his man and delivered the right ball to send Sosaia Feki over to hand the Sharks their first lead of the night.
Antonio Winterstein had got the game's first try on 12 minutes, scoring just inside the left corner off a Coote cut out pass.
Ray Thompson then sent Kyle Feldt streaking away down the right sideline before the Cowboys winger passed back inside to send Ben Hampton in for the try.
Just before the interval, the home crowd were stunned again as a Michael Morgan grubber somehow resulted in a 40/20, with the five-eighth turning provider from the ensuing set to set up Feldt with a pinpoint kick that he did well to ground.
The Sharks are 7/10 to win their next game against Canterbury, who are 6/5.
Cronulla are 93/100 conceding a 6.5-points start.
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