Two goals from Eric Odhiambo helped the Tanandice second string to a thoroughly deserved three points at Station Park, Forfar against a reasonably strong Tynecastle side.
It was a game in which both side had plenty of chances, with the difference being that United took theirs and Hearts didn't.
But United had to come from behind, Finnish striker Juho Makela slotting home the opener after being sent clear with only five minutes gone.
However, ten minutes later good build up work on the left between Eric Odhiambo and Steven Robb enabled the latter to cross for Jon Daly to squeeze in the equaliser at the near post.
Five minutes from the interval, a superb individual goal from Odhiambo saw United go in front. Collecting the ball outside the box, he twisted and turned, evading two or three challenges in the process and just when he looked to have lost his chance steered the ball into the far corner from ten yards.
Seven minutes after the re-start, the visitors levelled more by good fortune than design. Deividas Cesnauskis played the ball through to Makela who mis-control sent the ball careering up and over new Tannadice custodian Kemoko Camara.
Two minutes later the Guinea goalie kept out a Jose Goncalves effort with his legs.
And three minutes later, there was a quite astonishing miss by Mark Cown who somehow guided the ball past the post from inside the six-yard box with the goal at his mercy!
Hearts were made to pay for those misses when Danny Swanson swept home a free-kick from 25-yards after Jon Daly had been fouled.
An offside flag prevented Ross Hamilton from getting a leveller for the visitors and five minutes later their fate was sealed when United scored a fourth with eight minutes left.
Sean Fleming did the spadework, putting Odhiambo in on goal and the on-loan striker from Leicester City coolly lobbed the ball over the advancing keeper to hit the bar and post before nestling in the back of the net.
Right on time Odhiambo ought to have completed his hat-trick firing just over after Ryan McCord played him in on the keeper.
Dundee United: Camara, Milligan, Fleming, Dillon, Pope, Ryan McCord, Paterson (J Russell 62), Swanson, Daly, Odhiambo, Robb (Ross McCord 70). Subs not used: Gibson, McGrath.
Hearts: Basso; Thomson, Goncalves, Kancelskis (Hamilton 70), Divine; Screpis, Ivaskevicius, McCann, Ksanavicius (Cowan 46), Cesnaukis (Husband 66); Makela. Subs not used: Bjornsson, Kelly, Mearns.
Referee: W Hornby.