Play-off hopefuls Wrexham looked to have clinched only their third away win of the season through Blackburn Rovers' loan striker Matt Derbyshire.
Derbyshire grabbed his second two-goal haul in five days as a lacklustre game suddenly sprung to life with four goals in 16 minutes at the start of the second half.
The Stags were given a lifeline in the 64th minute, three minutes after Derbyshire's second goal. Danny Williams tripped substitute Simon Brown on the edge of the area and Barker rifled in from the penalty spot.
Remarkably the home side then levelled within three more minutes, the towering Barker powerfully heading in a deep cross from substitute Gus Uhlenbeek for his 19th goal of the season.
And in a thrilling finish the Stags went close to a winner on five occasions, the best chance falling to defender Jake Buxton whose injury time header was saved under the bar by Michael Ingham.
Wrexham had gone close a goal in the opening minute when Andy Holt's 30-yard free kick was well held by keeper Kevin Pressman.
The veteran then twice almost gifted the visitors the lead. First his poor clearance fell straight to Mark Jones, but with an empty net gaping Jones' first time shot was deflected for a corner.
From that flag-kick Pressman spilled the cross, but Dennis Lawrence failed to punish the error.
Barker's divine header from an Alex John Baptiste cross was well held by Ingham as the Stags hit back and then Danny Reet's first time drive shaved the bar.
The best chance of a poor half fell to Wrexham's Simon Spender whose 39th minute shot rebounded to safety off the foot of the post from a Holt cross.
But there was no let off for the Stags. Six minutes into the second half Buxton's woeful back pass inside the penalty area gifted Derbyshire the easiest of chances to round the keeper and score.
Less than 60 seconds later Mansfield should have levelled, but Reet's 15-yard shot lacked power and Ingham comfortably saved.
That miss appeared to be vital when Derbyshire doubled the Dragons lead in the 61st minute, racing clear onto a clever flick on from Sam Williams and firing under Pressman. But then the Stags came storming back to snatch a point.