A first-half double from Scott McDonald helped Motherwell leapfrog Aberdeen into seventh spot as the visitors' miserable run continued.
The striker's first flew in with the aid of a deflection and the second was forced over the line from close range.
After the break Alan McCormack capitalised on some shoddy defending to shoot home at the second attempt.
Aberdeen were absolutely wretched throughout the game but substitute John Stewart grabbed a late consolation.
The defeat continues Pittodrie manager Jimmy Calderwood's woes and supporters' boos again rang out at half-time and full-time.
Aberdeen badly needed an early pick-me-up following dismal 0-0 draws with Livingston and Dunfermline in their last two outings.
Stevie Crawford had an early shot but it was beaten away by Motherwell keeper Graeme Smith.
But the home side were ahead after nine minutes when McCormack fed Jim Hamilton, who in turn sent strike partner McDonald one-on-one with Pittodrie captain Russell Anderson.
There seemed little on when the Australian drove in a shot but a heavy deflection off Anderson wrong-footed keeper Jamie Langfield and allowed the ball to spin into the net.
Things went from bad to worse for Aberdeen in the 26th minute when they lost a calamitous goal.
The Dons repeatedly failed to clear a corner and Richie Foran benefited from a hopeful cross which found him lurking at the back post.
When his header ricocheted back off Chris Clark, the Irishman powered a volley past Langfield's attempted block and the lurking McDonald forced the ball over the line from only inches out.
Two minutes later the visitors' rearguard allowed Hamilton's tame cross to slip through to Foran but the midfielder should have done better than scoop his volley over from six yards.
McDonald then turned Zander Diamond inside out before powering in a drive which Jamie Langfield turned away from his top corner.
Langfield then had to dive low to his left to turn aside McCormack's well-placed header in the 41st minute and then stop McDonald's shot in first-half injury-time.
McCormack had another header from Steve Hammell's cross turned away by a busy Langfield at the start of the second period but he was not to be denied in the 53rd minute.
Foran's chipped pass saw Anderson dither and Kevin McNaughton fluffed his attempted pass back.
McCormack nipped in to poke a shot goalwards and, when Langfield's save rebounded kindly for the midfielder, he stroked the ball into the unguarded net.
Langfield denied McDonald what would have been a deserved hat-trick in the 62nd minute before coming to the rescue yet again two minutes later - although he did not appear to know much about the save.
Brian Kerr's cross was nodded into the goalmouth by Hamilton but Langfield somehow blocked Brian McLean's point-blank header.
Quite out of the blue Dons substitute Stewart pounced to flick Crawford's cross past Smith as the clock ran down.
Motherwell: Graeme Smith, Corrigan, Craigan, McLean, Hammell, Kerr, O'Donnell, McCormack (McBride 80), Foran, Hamilton (Coakley 89), Scott McDonald (Clarkson 84). Subs Not Used: Meldrum, Paul Quinn, Fagan, Fitzpatrick.
Goals: Scott McDonald 9, 26, McCormack 53.
Aberdeen: Langfield, McNaughton, Anderson, Diamond, Muirhead (Mackie 38), Smith, Nicholson, Dempsey, Clark, Lovell (Stewart 69), Crawford. Subs Not Used: Esson, Winter, Foster, Considine, Macauley.
Goal: Stewart 90.
Ref: C Murray