NSW were far from perfect, but unlike last week's humiliation against the Western Force, Michael Foley's men backed themselves with the ball in hand to fight back against the South Africans and score four tries.
Sharks star hooker Bismarck du Plessis scored a soft try in the 49th minute to put his side up 24-13 and the signs were ominous.
But tries to fullback Bernard Foley and Carter got the Waratahs into the lead.
When Lambie's late penalty put the Sharks into the lead heading into the final five, it would have been easy for the Waratahs to throw in the towel.
But Berrick Barnes, in his first game at five-eighth for the year, showed a touch of class to get out of trouble on his own line from a kick-return and set the foundation for the final roll of the dice.
Mumm surged up the field, and after the Waratahs were awarded a scrum, they managed to open up some space a couple of rucks later down the right for Kingston to sneak over for the match-winner.
In his first ever starting match for the Waratahs, No.9 Brendan McKibbin was awarded man-of-the-match, for a first-half try and a flawless display with the boot.
The Waratahs managed to avoid an embarrassing third straight loss at home, and can now look to get their season back on track.
-AAP