Brown's 76th-minute one-pointer was against the grain in Newcastle, where the Dolphins dominated possession and territory in the second half as they hunted a ninth straight victory.
It was the Dolphins' first loss since being beaten in Wellington by the Warriors on Anzac Day.
"That's an example of a big player in a big moment, and he delivered for us," Newcastle coach Justin Holbrook said.
"He slotted it like he's kicked 100 of them, and it was his first."
Averaging 35 points over a club-record run of eight wins, the absence of Dolphins halfback Isaiya Katoa (wrist) and State of Origin quintet Hamiso Tabuai-Fidow, Tom Flegler, Max Plath, Jack Bostock and Selwyn Cobbo was telling.
The Dolphins were restricted to two tries by a determined Newcastle defence.
"I was happy with the effort and that we tried really hard," Dolphins coach Kristian Woolf said.Â
"There's a couple of things we can clean up that will give us more opportunities, but overall I'm not disappointed with the performance at all.
"We have shown through the whole period what the entire group is capable of, and while they're disappointed with the game, they're really proud of what they have done throughout the Origin period."
Already reeling from the late withdrawal of Trey Mooney, the Knights' front-row stocks took a further hit when Jacob Saifiti was ruled out after 14 minutes with a hamstring injury.
Dumped by NSW for the State of Origin decider, Newcastle back-rower Dylan Lucas shrugged off his demotion with the game's first try after hitting a neat "unders" ball from fullback Fletcher Sharpe to go over untouched from 30 metres out.
Newcastle doubled down just before halftime when Fletcher Hunt bested counterpart centre Jake Averillo, putting the Knights ahead by 12 at the break.
The Dolphins showed glimpses of their usual form in the second half and hit back early when Jamayne Isaako crossed in the corner to post the first points for his side.
Newcastle junior Kurt Donaghue then came back to haunt the Knights, starting and finishing a neat backline movement to put the Dolphins back within two.
A Jermaine McEwan high shot on Dolphin Connelly Lemuelu gifted the visitors a penalty goal to square the ledger in the 68th minute.
But Brown enjoyed the last laugh, polishing off Newcastle's best chance of the second half to kick the game-determining field goal.
Victory places Newcastle firmly in the NRL's top four after 18 rounds, a stark contrast to last season's wooden-spoon finish.
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