St Mirren salvaged a point from their trip to Tannadice but still slipped out of the Premiership top-six.
Dundee United striker Steven Fletcher used all his experience to fire the Terrors into an early lead, slotting home a volley expertly from the edge of the box.
The Buddies battled back into the game and thought they'd levelled in the second half when Richard Taylor's header rustled the back of the net.
