The Arsenal great netted a hat-trick and set up another goal as Hans Backe's men made it nine goals in two matches at home after a losing start to the campaign.
The Impact took the lead in the 18th minute when Sanna Nyassi pounced on a defensive error from Swedish centre-back Marcus Holgersson to fire past Ryan Meara ten minutes before Henry grabbed his first with a back post header from Rafael Marquez's rightwing cross.
Montreal managed to edge in front in the 38th minute when Meara was beaten at the near post by Justin Mapp's relatively tame right-footed effort from the edge of the area but in stoppage time of the first half, the Red Bulls leveled again when Kenny Cooper converted from the penalty spot after Dax McCarty had been adjudged to have been brought down by Matteo Ferrari.
Just over ten minutes into the second half, Henry gave New York the lead when he fired home a brilliant shot on the turn from the top of the box before Mehdi Ballouchy gave the home side a two-goal cushion in the 72nd minute with a simple finish from a deft Henry flick-on after Jan Gunnar Solli had skinned his man on the right flank.
The win was wrapped up with a minute to go in regular time when Henry followed up Cooper's initial effort which was saved by Donovan Ricketts to dink over the Jamaican gloveman to record his first MLS treble.