Having not lost in their opening nine games at Tannadice Park, the Tangerines, with five first-team players missing, struggled to find any rhythm and in the end posed little threat to Craig Brewster's men.
The Caley Thistle manager, who was unable to turn around the Tayside club during his short spell as boss, must have been delighted by the spirit of his players as they out fought Craig Levein's troops.
But, in truth, it was not difficult for United were, quite simply, poor.
Against the run of play, the visitors had grabbed the opener in the 20th minute taking advantage of a rare mistake from Grzegorz Szamotulski.
With little threat on the horizon, Ian Black had the vision to see the keeper well off his line and his 25-yard shot over the keeper went straight into the net for the first goal United had lost at home in open play this season.
United, with so many changes in their line-up, fell into the trap of the long ball game and were really at sixes and sevens throughout, giving their hosts every encouragement with poor passing and little forward threat.
Any chances for the hosts came from dead balls with Garry Kenneth missing three easy headers over the period.
After a lethargic opening 45 minutes, Jordan Robertson began the second with an excellent curling shot from 25 yards which went narrowly over.
Then came an astonishing miss from Kenneth in the 57th minute, as he headed wide from only six yards added more frustration for the home support.
United continued to push for the equaliser, but the Highlanders almost grabbed a second with their breakaway ending when John Rankin's shot had the United keeper in a flap and was almost punished.
United pushed hard in the last 15 minutes but it was not to be their day and Brewster left with a rare victory as a manager at Tannadice.