Steven McGarry testing Jamie Langfield from long range before the home side opened the scoring in the tenth minute.
The goal was a personal triumph for Jim O'Brien, who linked firstly with Paul Quinn and then David Clarkson before hitting a deflected shot past a stranded Langfield.
Aberdeen provided little threat in the first period, being reduced to only a couple of feckless long-range efforts from Charlie Mulgrew and Derek Young.
The only problem with Well's first-half performance was their inability to turn their dominance into goals with Quinn being the worst offender when he sent a free header wide from ten yards out.
Aberdeen looked lively at the start of the second half, but it was still Motherwell who were the more dangerous in front of goal. Clarkson saw two shots go narrowly wide, while Brian McLean headed a corner just over.
Motherwell were almost made to pay for these misses when Graeme Smith was forced to save from a stinging Sone Aluko drive, but on 68 minutes, the Dons did make Motherwell pay for their misses when they equalised.
A Scott Severin long throw was flicked on by Lee Miller to Chris McGuire, who swept a shot past Smith and high into the net off the underside of the bar.
The visitors were then given an uphill task when they were reduced to ten men with 20 minutes left on the clock.
Defender Andrew Considine had needlessly been booked for dissent before seeing a second yellow for a rash challenge on Clarkson.
The game died after this with the visitors forced to sit in and frustrate the home side, although it took a stunning save in stoppage time from Langfield to ensure a point went north.