New Aberdeen manager Steve Paterson learned how big the task ahead of him is as his side fell meekly at East End Park.
Aberdeen contributed to their own downfall as they gifted Dunfermline their goals and the game was over as a contest by midway through the second half.
Steve Crawford opened the scoring late in the first half, Jamie McAllister headed the second into his own net in the 47th minute and then Craig Brewster scored from the penalty spot.
But Aberdeen were too easily brushed aside and they allowed Dunfermline to dictate the pace from the outset.
Jason Dair had the first serious effort of the game when his right-foot shot from 25 yards flew narrowly wide.
Aberdeen were rarely seen as an attacking force but McAllister was not far away with a free-kick which dipped just over the crossbar.
Laurent D'Jaffo had another effort after a poor defensive clearance from Andrius Skerla but Derek Stillie had it covered.
Aberdeen fell behind six minutes from the break after gifting Dunfermline the opening goal.
Russell Anderson misjudged a throw-in and Brewster pounced and threaded the ball through for Crawford to beat Davie Preece with a crisp, right-foot shot from 16 yards.
Two minutes into the second half, Aberdeen leaked another avoidable goal when Dair's corner was headed into his own net by McAllister.
It left Aberdeen with an uphill battle. A Darren Young volley was headed just a foot over by Darren Mackie as Aberdeen briefly threatened to come back into it.
But it was Dunfermline who almost snatched a third in the 52nd minute when Barry Nicholson met a Scott Thomson cross with his head but Preece held his effort.
Dunfermline went three up in the 63rd minute after Derek Young tripped Thomson in the penalty area.
Brewster sent Preece the wrong way with the spot-kick. D'Jaffo and McAllister had chances to reduce the deficit after that but lacked conviction with their finishing.