Kalyn Ponga slotted a sideline conversion after winger Greg Marzhew scored with two minutes remaining to give Knights fans a glimmer of hope at Ocean Protect Stadium on Friday and send shivers through the Sharks faithful.
But it was all in vain for the visitors, who suffered a second two-point loss in as many weeks after going down to South Sydney 26-24 in round 19.
"We tried hard and created enough chances, so I'm really disappointed we didn't get the win," Knights coach Justin Holbrook said.
In contrast, it was the third straight win for Craig Fitzgibbon's men, who are on course for a fifth finals appearance in a row.
Newcastle hadn't won at Shark Park since 2014 and Cronulla hold the impressive record of 13 wins from their past 14 in the Shire.
"We hustled pretty hard," Fitzgibbon said, contrasting the 66 points via 11 tries scored against the Dolphins last round, but only scoring three against the Knights.
"To come out of a win like that, get behind the eight-ball (first half) and then get going again in the second, I'm pleased with that."
The only concern is a left pectoral injury to NSW and Tonga prop Addin Fonua-Blake, which saw him leave the field in the 24th minute and only return for a brief stint in the second half.
"I was a bit worried about putting him back out there, but the medics told me it would be all right as it's a low-grade pec strain,'' Fitzgibbon said.
"Obviously you don't want to make it a high-grade strain, but he told me he was good to go."
Newcastle remain entrenched in the top eight despite their third defeat in six games, with the Sydney Roosters up next.
Tit-for-tat tries in the first half on Friday saw the lead change four times.
The hosts took a 14-12 advantage to the break through the more accurate boot of Nicho Hynes (three from three), while Ponga missed both of his attempts.
That was in keeping with recent form, after Hynes kicked all 11 conversions in the 66-0 demolition of the Dolphins last weekend.
Sheer speed to get around defenders saw Ponga open the scoring on the right edge with the match only eight minutes old, before swinging to the left and attracting enough defenders for Marzhew to cross untouched.
Sharks fullback Will Kennedy and winger Sione Katoa were joined on the try-scorers' list in the second half by Ronaldo Mulitalo, who gratefully accepted a floating Hynes pass and crossed in the corner to push the score out to 20-12, the biggest lead of the night.
Newcastle rallied late and second-rower Francis Manuleleua scooted to the right corner post in the 70th minute, but couldn't ground the ball under a sea of Cronulla defenders.
But the eight-point buffer proved the lifesaver after another Marzhew effort in the 78th minute.
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