Elder has joined the Dons from Shrewsbury until the end of the season
Debutant Nathan Elder scored one goal and made another as AFC Wimbledon saw off play-off rivals Mansfield and moved above them into fourth in the table.
Elder headed the opener in at the far post from a fine curling cross from Will Hendry after just two minutes.
Stags then had their best spell of the match with Gary Silk, Kyle Perry and Rob Duffy all going close.
But the home side doubled the lead when Lewis Taylor swept in a superb left-foot strike from Elder's clever header.
The visitors enjoyed long spells of pressure after the break but failed to create many clearcut opportunities.
Jake Speight did put the ball in the net with a deft lob after racing through in the closing stages but he was flagged for offside.
And Stags debutant Jon Shaw also hit the post with a scrambled effort after a fine team move in injury team.
At the other end Elder, who joined from Shrewsbury this week, could have added a second but was thwarted by some superb last-ditch defending by Michael Brough.
Ricky Wellard also went close with a blistering strike but the Dons were not to be denied and leapfrog the Stags in the Blue Square Premier.
AFC Wimbledon: Brown, Hatton, Judge, Johnson, Blanchett, Taylor, Adjei, Hendry (Conroy 80), Poole (Wellard 75), Elder (Montague 84), Main. Subs Not Used: Pullen, Kedwell.
Bookmark with:
What are these?