Motherwell had only won once since the opening day, prompting the resignation of Stuart McCall on Sunday, and there looked to be little sign of respite as United bossed the opening period.
But caretaker boss Kenny Black ensured a reinvigorated home side emerged for the second half and Iain Vigurs’ deflected strike was enough to secure the win and lift them above St Mirren to 10th place.
Aidan Connolly, one of the latest in a line of promising youngsters being schooled at Tannadice, was the shining light of the first 45 minutes, a constant thorn in the side of the home defence.
He fired an early free-kick over the bar before delivering an excellent cross towards a lunging Ryan Dow who was inches away from opening the scoring.
The United schemer then picked out his former Queen’s Park team-mate Blair Spittal bursting into the box, but the latter’s finish under pressure slipped narrowly wide.
Chris Erskine was the next to work Dan Twardzik in the home goal but the Motherwell goalkeeper was helpless as the irrepressible Connolly skipped past him – only to fire against the post from eight yards.
The half concluded with Twardzik showing his dexterity to keep out a deflected Connolly effort, Henrik Ojamaa having offered the home side their only crumb of comfort with a wildly-sliced goal attempt.
But ‘Well were a different proposition afger the break, Lionel Ainsworth cracking a shot off the goalframe when Radoslaw Cierzniak could not gather Craig Reid’s initial attempt. Moments later Keith Lasley teed up Vigurs and his shot took a small deflection on its way past Cierzniak (52).
United looked stunned and the home side thought they had doubled their lead when Ainsworth flicked the ball into the net but the assistant referee deemed otherwise.
Gary Mackay-Steven and Nadir Ciftci entered the fray but the momentum remained with the home side, Ojamaa the next to go close with a cracking strike.
United’s Conor Townsend headed wide when well placed and John Rankin was foiled by Twardzik in a late flurry but it was not enough to prevent Jackie McNamara’s side slipping to a third straight away defeat.