Played in horrendous, windy, icy conditions on the 4G pitch at Mansfield, it was a difficult game for both sides.
Scunthorpe had a very young team and two of the trialists who came into the side did really well on the day, scoring the goals that secured the victory.
With United playing against the wind in the first half, the Stags were in the ascendency for long periods of it.
After 15 minutes, the Iron had their first attempt on goal when Jack Moore-Billam shot just wide.
The visiting team managed to take the lead on 40 minutes when trialist Harrison Poulter closed down the home centre-half, won the ball from him and rounded the goalkeeper to score from a tight angle.
The Iron came out strong at the start of the second-half when Harry Lewis whipped in a free-kick that went just wide.
Mansfield levelled on 68 minutes, from a corner and scoring a free header.
Two minutes later, the Stags went ahead as United switched off and the home team scored out of nothing. From being in control, the Iron were now 2-1 down.
Soon after, Poulter was played through but the ball didn't come down for him in time and he couldn't get his shot away in a good position.
In the 76th minute, Scunthorpe levelled when Trialist A picked the ball up on the edge of the box, took a great first touch and beat his man before firing into the far corner.
On 84 minutes, after pushing to try and win the game, Cameron Wilson's free-kick deflected off a Mansfield player out for a corner, and from the resulting set-play United scored to make out 3-2 as Trialist A converted at the back post after the ball went over everyone else.
Mansfield threw everything at the Iron to try and level but United held on for the win.
"It was a really pleasing result, especially with the changes we had to make to the team," said Professional Development Phase Coach Steve Thornber.
IRON: Balme, Franklin, Kemp, Lewis, Lobley, Moore-Billam, Wilson, Moore, Cribb, Trialist A (Strouther, 89), Poulter.
IRON SUBS NOT USED: Trialist B, Trialist C, Foster.