It was the visitors who enjoyed the better of the early stages and they went in front after 18 minutes when winger Kris Commons curled a shot into the far corner after a surging run into the box by Jack Lester had been blocked by goalkeeper Joe Murphy.
A minute later, Scunthorpe might have been back on level terms when a shot from the edge of the box by striker Jermaine Beckford almost caught Forest keeper Paul Smith by surprise.
The home side failed to capitalise on a series of free-kicks in and around the box as Forest defended their lead.
But Scunthorpe made a flying start to the second half and were back on level terms in the 46th minute.
It was leading marksman Billy Sharp who poached the equaliser with his 25th goal of the season from a left-wing cross from Matthew Sparrow.
Sharp then missed a golden chance to put Scunthorpe in front when he headed wide with the goal at his mercy.
Forest had another escape when a close-range shot from Sparrow was blocked almost on the line after a right-wing cross from Cleveland Taylor had sliced open the visiting defence.
United were much the better team in the second half, but it was Forest who almost snatched a winner when midfield man Lewis McGugan let fly from 20 yards with a shot that keeper Murphy blocked away with his legs.