The sell-out crowd witnessed a game with plenty of hard work, fouls and competitivenes, while there was a lack of quality at times.
Ian Harkes came up with the defining moment, turning on the edge of the box to fire past Adam Legzdins. There were some big performances for the Tangeroines, especially in defence and midfielder Jeando Fuchs.
It is the latest big win for Thomas Courts this season after victories over double winners St Johnstone and Scottish champions Rangers.
How did the United players rate out of ten?
Player ratings scale - 10: One of the best performances you've seen. 9: Outstanding. 8: Very good. 7: Good. 6: Average. 5: Poor, 4: Very poor. 3: A terrible day at the office. 2: Abysmal. 1: One of the worst performances you've seen.
5. Scott McMann - 7
Won the battle in the main with the tricky McMullan, although did pick up a booking. Looks a dependable left-back after deadline-day move from Hamilton. Photo: Ross Parker - SNS Group
6. Calum Butcher - 5
Captain committed too many fouls and was rightly booked in the first half. Replaced by Dylan Levitt at the break. Photo: Alan Harvey - SNS Group
7. Jeando Fuchs - 8
Head-and-shoulders above every other player in midfield. Excellent tackles and extremely tidy in possession. Photo: Roddy Scott - SNS Group
8. Ilmari Niskanen - 5
Finn flitted between wide right and behind striker but struggled to get any change out of the Dundee defence on his first start for the club. Subbed on 59 minutes. Photo: Roddy Scott - SNS Group