St George Illawarra's Morris twins combined for the clincher as the Dragons pipped Manly 20-18 in a seesawing NRL clash at Brookvale Oval.

The Dragons scored four tries to three, including the 75th minute clincher to fullback Brett Morris, to score the upset victory and take their record against the Sea Eagles to seven wins from their last eight games.

Down 18-14 with five minutes remaining, centre Josh Morris stepped cleverly and sent a ball to twin brother Brett who crashed over.

Jamie Soward's conversion completed the two-point win.

The Dragons scored tries through Beau Scott, Ben Hornby, Jason Nightingale and Morris while Soward kicked two goals from four attempts.

For the Sea Eagles, David Williams, Steve Menzies and Michael Robertson crossed for four-pointers with Matt Orford booting three goals in front of 12,058 fans.

Manly led 12-10 at halftime after both sides had scored two tries in the first half.

But the Dragons re-took the lead 14-12 with a controversial benefit of the doubt try in the 54th minute.

Winger Nightingale and second-rower Lagi Setu both looked to gather in a Soward cross-field bomb and video referee Phil Cooley saw no clear evidence their multiple touches had constituted a knock-on and allowed the try.

Manly looked to have regained the lead in the 66th minute when Menzies took an inside ball and shredded the Dragons defence on the way to the line but the veteran tryscoring machine came up with a rare error, dropping it as he crashed over.

But the Sea Eagles didn't have to wait long to hit the front, penalties against the Dragons providing the field position and Robertson grabbing an Orford chip after Chase Stanley had taken an embarrassing airswing.

The Eagles will rue being denied by Cooley three minutes later when the video referee ruled Brett Stewart had not grounded a Robertson grubber.

The Dragons went into the match without NSW centre Matt Cooper, who failed to back up from Wednesday's State of Origin clash because of a minor back complaint.

"It's what you play footy for, to get the tries when you need them," Brett Morris said.

"I just popped up there, it was a good pass."

But he denied telepathy between the sons of former Dragons half Steve Morris had come into it.

"It's just having those years playing footy together, we just know each other's game so I just showed up where he wanted me and it turned out good," he said.

Dragons coach Nathan Brown paid tribute to re-signed half Soward after he booted home the conversion that sealed the win.

"His self-esteem's a bit higher and I think maybe six or eight months ago we might have said give Gaz (Mark Gasnier) or Benny Hornby the kick but because he's a lot more confident person now it was never thought of," the coach said.

Brown credited his side's character in the scrappy contest, in which each side only completed around 70 per cent of their sets, and admitted the Menzies and Stewart no-tries had seen the football gods smile on his team.

"We hung in there and we're a much tougher team this past five weeks than I think people give us credit for," Brown said.

Manly came into the night's contest in second place but captain Orford said his side didn't deserve that ranking.

"Until we learn to, after a try, back-up and just get to our kick and once we've got our foot on the throat just go on with it, we can't put ourselves up on a pedestal as a top team," Orford said.

"There's still a long way to go and we haven't learnt that yet."