The Imps appeared to be heading for three points after grabbing a goal against the run of play early in the second half.
But with time running out Mansfield pressed forward and substitute Simon Brown was fouled by Lee Beevers on the edge of the box.
Midfielder Allan Russell struck the 90th minute free kick into the bottom corner despite the efforts of the Lincoln defensive wall in front of him.
The goal earned a draw for in form Mansfield from a scrappy local derby in which neither team could master the blustery conditions.
Lincoln went close early on when Marvin Robinson was inches away from connecting from a cross from his name sake Steve Robinson.
But Mansfield quickly took control and went close with two long-range efforts from central midfield man Giles Coke.
Gus Uhlenbeek caused Lincoln problems throughout the first half and should have scored five minutes before the break.
The midfielder burst past two defenders and cut in from the right flank, but sent his final shot straight at Lincoln keeper Alan Marriott.
A minute later Uhlenbeek cut out the Lincoln defence with a short corner to Adam Rundle. The winger wasted the chance by slicing his effort wide.
Another superb pass from Uhlenbeek sent Rundle clear in the 50th minute. The winger beat his man and sent in a low cross which was fumbled by Marriott.
The ball fell to Danny Reet but from 10 yards out he shot over with the goal at his mercy.
Lincoln hit back almost immediately and went in front in the 53rd minute.
A cross from Colin Cryan was cleared straight to Francis Green whose low drive went straight through the legs of Kevin Pressman.
Mansfield stepped up their efforts. Richie Barker sent a free kick over the bar from 25 yards and then Coke headed wide from in front of goal.
But after Russell's last gasp leveler, the Imps had a great chance to snatch victory deep into stoppage time.
Jamie Forrester was sent clear but his chipped shot brought a superb save from Pressman.