The Stags were cruising at 2-0 when Bees boss Paul Fairclough gambled with three changes, and they all paid off, with former Mansfield striker Adam Birchall doing the damage with a 77th-minute equaliser.
Mansfield, who squandered a hatful of chances, will look back to when Jefferson Louis headed against the post when they led by two goals as the turning point - not just in the match, but possibly in their bid to stay in the Football League.
The draw stretched Town's unbeaten run to three matches, but it leaves them still three points from safety.
The Stags, lifted by their midweek win against Wrexham, started off like a train - pouring forward at every opportunity. Matt Hamshaw's curling cross-shot almost caught out keeper Lee Harrison and then Louis failed to get on the end of the winger's cross.
Barnet, hit by injuries to three of their usual four defenders, held on though and posed their own threat through Albert Adomah. The Bees winger tested the home defence with his pace, one shot after a weaving run only being blocked by diving full-back Gareth Jelleyman.
But in the 14th minute the Stags made the breakthrough. Michael Boulding and Louis combined cleverly with a neat interchange of passes on the edge of the area and Boulding raced in to finish past the diving Harrison - his 22nd goal of the season.
A minute later a raking run and cross by Boulding almost picked out the unmarked Louis at the far post as Mansfield looked to double their lead.
Louis again went close in the 22nd minute, grazing the outside of the post with a low 12-yard shot when well-placed.
The Bees almost punished the Stags for not grabbing a second goal when Adomah, a constant threat, curled narrowly wide from 20 yards.
Then, in first-half stoppage time, Hamshaw's clever 18-yard lob landed on the roof of the net with Harrison beaten as Town finished the half on top.
Barnet started the second period the brighter though, Max Porter dragging a shot wide from 20 yards.
But Mansfield were soon back on top, Hamshaw leading a quick break which ended with Boulding's low shot being pushed away for a corner by the sprawling Harrison. Then the striker's 20-yard drive was deflected for a corner as the pressure mounted.
In a rare second half Bees breakaway, their lone threat - Adomah - was denied an equaliser by the acrobatics of keeper Carl Muggleton.
And that proved vital as, seconds later in the 55th minute, Hamshaw finally doubled the home team's advantage, lobbing the ball home after collecting a deep clearance on his chest.
Louis should have made victory secure 11 minutes later, but his firm downward header from Boulding's cross hit the foot of the post.
And seconds later Barnet were back in contention, substitute Anthony Thomas firing in from 15 yards with his first touch after a triple substitution.
Nathan Arnold's low drive was saved by Harrison in driving hail and snow as Mansfield tried to secure victory.
That save was made to look crucial in the 77th minute when substitute Jason Puncheon's free-kick hit the post with Muggleton motionless and substitute Birchall reacted the quickest to knock in the rebound.
Substitute Simon Brown squandered a great chance to snatch a late winner for the home side, but his 12-yard finish was deflected wide for a corner.