Aberdeen started brightly and Graeme Smith in the home goal was forced to save early on from Stevie Crawford. The Dons looked sharper in the early stages but were stung when the home side took the lead in the ninth minute.
Alan McCormack won a loose ball before feeding Jim Hamilton, who slid in Scott McDonald at the edge of the box. The striker hit a shot which cannoned off Russell Anderson and deceived James Langfield in the visiting goal.
The game was turned on its head as Motherwell went on to dominate the proceedings. McDonald and Hamilton combined to cause all sorts of problems for the visiting defence.
There was no surprise when Well extended their lead on 26 minutes after a Brian Kerr cross was missed by the Dons defence, leaving Richie Foran time to shoot.
Langfield made a half-save and McDonald was on hand to hammer the ball home from a yard out.
McDonald could've had a hat-trick before half-time but Langfield did well to save from the Aussie striker on a couple of occasions.
The second half started in the same vein as the first had finished, with Motherwell pushing forward and taking their lead to three.
A hopeful pass from Foran was left by Kevin McNaughton and Anderson, allowing McCormack to nip in. The midfielder's first effort was saved by Langfield but he latched onto the rebound to score from close range.
As the half wore on Motherwell looked likely to add to their lead and Langfield pulled off a stunning save to deny Brian McLean from a close-range header.
The hosts took their foot off the gas and the Dons were spared any additional blushes as the game wound down to a deserved win for the home side, despite a late consolation for Aberdeen when John Stewart turned a Crawford cross home from close range.