There was a real ding-dong battle throughout with United taking advantage of ten-man Aberdeen and ultimately should have won by a far greater margin.
The Tangerines had started the better and missed several chances and had two penalty claims waved aside.
It took Aberdeen fully 15 minutes to create their first chance with ex-United man Lee Miller heading straight into the arms of Derek Stillie.
The keeper subsequently foiled a further two efforts from the striker and breathed a sigh of relief in the 27th minute when Gary Dempsey's curling 25-yard free-kick came down off the underside of the bar.
With a more attacking formation after the break, the Dons grabbed the lead in the 56th minute when another Dempsey free-kick was hammered home at the far post by Scott Severin.
But the Aberdeen lead was wiped out five minutes later when Barry Robson's curling free-kick was nodded in by Collin Samuel from eight yards.
It was now full steam ahead for the home side as the shots rained in on Jamie Langfield's goal.
Then the under pressure the keeper brought down David Robertson in the box for Robson to convert and Samuel wrapped it up in the final minutes with a killer third.