Stevenage kept their play-off hopes alive thanks to an injury-time winner from loan star Ilias Chair.
Kurtis Guthrie gave Boro the lead at the One Call Stadium, only to see Tyler Walker get the Stags back on terms.
But QPR youngster Chair further endeared himself to the Stevenage faithful to ensure they will go into their last match of the season still in with a chance of climbing into the top seven.
Boro boss Dino Maamria named an unchanged starting line-up from the Easter Monday draw with Exeter City but saw Michael Timlin pick up a yellow card with only three minutes played.
Chair saw a shot blocked by Matt Preston moments later, before Paul Farman produced an important stop at the other end to prevent Malvind Benning’s free-kick creeping in at the near post.
Farman got down to his right to push Willem Tomlinson’s shot behind for a corner, after a neat flick from Jacob Mellis on 16 minutes,
But Boro had a great chance to open the scoring midway through the first half when Scott Cuthbert’s flick on the edge of the box found Timlin, who teed up Ben Nugent, but his shot was saved by Logan.
And the visitors were inches away moments later as Terence Vancooten’s floated cross for Guthrie was intercepted by a Mansfield defender, who saw the ball hit the post and go behind for a corner.
The set-piece then reached Timlin at the far post, but his scuffed shot was cleared by the hosts for another corner.
And after Guthrie had penalty claims waved away having gone down in the box, Boro almost took the lead on 31 minutes when Chair let fly from range, only to see Conrad Logan produce a fingertip save to keep the scoreline blank.
Emmanuel Sonupe fired a right-footed shot from outside the box wide of the left-hand post two minutes later, but CJ Hamilton then broke through and was taken down by Nugent, who escaped censure, before Benning’s free-kick was blocked and cleared.
Maamria’s men would have been disappointed to still be on level terms at the break, given the possession enjoyed and chances created in the opening 45 minutes.
And the Stags made a bright start to the second half, without seriously testing Farman, other than asking him to claim a series of crosses.
Sonupe dragged a shot on the turn wide on the target just before the hour mark, but Nugent did well to intercept Benning’s inviting cross and head behind, before substitute Danny Rose headed over for the home side.
Boro stunned the home crowd with 19 minutes left when Chair picked out Guthrie, who chested the ball down and volleyed past Logan to break the deadlock.
But the visitors were grateful to Nugent for a stunning block to deny Hamilton, after Farman had pushed out a shot from Mellis on 78 minutes.
Mansfield were back on level terms seven minutes from time, though, when Logan’s long kick caught the Boro defence out and Tyler Walker took advantage to net his 17th second-half goal of the campaign.
And it looked like honours would finish even until the second minute of stoppage time when Chair fired a right-footed shot into the bottom left corner of the net for a late winner to leave them two points off the play-off spots as they end their campaign with a home match against Cheltenham Town at the Lamex on May 4.
Stevenage: Farman, James-Wildin, Timlin, Cuthbert, Byrom, Sonupe (McKee 81), Chair (Wilkinson 90), Vancooten, Guthrie, Nugent, Martin. Unused subs: Byrne, Hunt, Revell, Gibson, Smyth.
Attendance: 6,390.
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