Star striker Richie Barker thought he had done enough to get three points for Mansfield with his 63rd minute strike and they should have killed the game off long before Hawley struck.
Young striker Nathan Arnold was unlucky twice in the last 15 minutes not to score his second league goal for the Stags.
And Barker was forced into the centre of defence for the last 15 minutes as Alex Baptiste and Jon Olav Hjelde limped off injured.
Carlisle top scorer Hawley headed over the bar in the second minute and Chris Lumsdon forced a good save out of Jason White in the 10th minute with a stinging volley.
Simon Brown mugged Zigor Aranalde on 18 but shot instead of passing to Barker who seemed to be in a better position and Mansfield didn't really have another chance in the first half.
Michael Bridges nearly snatched a 24th minute goal when his cross looped over White, but landed on the roof of the net. The striker then beat White afterwards only to see Baptise clear his shot off the line.
Ex-Stag Adam Murray then set Bridges up on 34 and the striker turned brilliantly and shot on target only to see the impressive White save again.
After the break Mansfield attacked more and got there reward on 63 when Gus Uhlenbeek found Brown in the box. The striker, making a surprise start as he had a hernia operation on Monday flicked the ball on and Barker was there to turn the ball over the line.
Kevin Gray headed wide on 75 for the visitors and Mansfield broke quickly on the counter attack with Arnold cutting into the middle and trying a speculative lob that dipped just over the bar.
In injury time Arnold played a neat one-two with Allan Russell, but the youngster blasted over when it seemed easier to score.
And Hawley gave them a lesson in finishing at the other end as he crashed home after White had made two great reflex saves to deny both himself and Bridges. White looked distraught as he picked the ball out of the net but Hawley celebrated clinching promotion.
The fans went wild and an attempted pitch invasion was halted by the arrival of police dogs in front of the stand.