Video referee Bernard Sutton watched more than a dozen replays before awarding a benefit-of-the-doubt try, extending the Tigers lead after an earlier Liam Fulton four-pointer.
Tigers utility back Beau Ryan and halfback Benji Marshall praised their classy fullback.
"That Dragons Army were getting into him and he had his little earmuffs on and he played very well. I'm proud of him," Ryan told AAP.
Marshall added: "I thought he really stood up tonight ... His most dangerous game is probably his running game so to see him run in that try just before halftime, I knew he was pretty switched on."
Moltzen denied his match-winning performance felt any better because it came against the team he refused to join in the off-season, despite signing a three-year deal last year.
But it was certainly a more impressive showing than his effort against them in round three at Kogarah this year when Moltzen had a forgettable afternoon - making three errors in a 36-12 thrashing.
"For me personally it was about doing my job for the team," Moltzen said.
"I could have been coming up against anyone and it wouldn't have been any different.
"All that stuff's in the past for me and this was just another game. I've moved on and just happy to get the two points."
The Dragons bolted to an early eight-point lead through unconverted tries to winger Brett Morris, who also scored in the second half, and hooker Mitch Rein after just 14 minutes.
The loss leaves the Dragons four points behind eighth spot with a poor for and against and just three matches remaining, but moves the Tigers to 26 points and potentially one win from securing a finals berth.
"We can (make the finals) but it's out of our hands," an exasperated skipper Ben Hornby said.
"Now we've got to hope for teams to win and teams to lose. Win all our games. We're in the position now where it's not in our hands."
Coach Steve Price wouldn't comment on the controversial Moltzen try but admitted to having frustration at their diminished finals chances.
"We put ourselves in that situation, we've got no one else to blame there but ourselves," he said.
Dragons five-eighth Nathan Fien was taken to hospital with a neck injury in the 50th minute with Jamie Soward finishing the game in the halves after starting on the bench.