Abo Eisa's stunning first-half goal secured an important second win in succession for United which pulled them out of League Two's bottom two, and their first victory at Port Vale since 2006 as they emerged 1-0 victors.
The Iron entered the game making two changes, as Jai Rowe and Harrison McGahey came in for Jordan Clarke, who was rested as a precaution, and Jacob Bedeau, who was on the bench.
The hosts pressed into on the right side of the area in the early stages and squeezed in a low cross. The Iron dealt with the ball before Junior Brown hooked clear.
There was then further good defending from Brown on four minutes as he intercepted from Tom Conlon’s left-wing cross into the area. The Iron got the ball clear with Emmanuel Onariase and eventually won a throw-in.
Vale then came forward down the right side, squeezing in a cross with Onariase clearing before the central defender did the same again soon after.
With 10 minutes played, David Worrall cushioned a header down to Mark Cullen, but McGahey read it and cleared. Soon after, the hosts got a free-kick on the left channel.
Worrall’s free-kick was a dangerous one, with Onariase emerging at the back post to head clear. A second cross came in with Legge heading goalwards, but Mark Howard made a comfortable save.
The 19th minute saw neat football from the Iron, from Rowe’s throw as he and Lewis Spence combined before the ball was fed into Ryan Loft. He was then picked up and thrown on the floor, but no free-kick was given.
Rowe then read Worrall’s first touch well to slide in and win the ball back as the hosts came forward following a move from the Iron which saw Alfie Beestin involved.
Soon after, Spence’s forward run saw him gain possession inside the area on the left. His low cross searched for Loft but Legge came across and headed clear.
Then, Loft hooked clear an inviting cross into the Iron penalty area, with the United forward back on defensive duties following a free-kick to the hosts. Soon after, Loft received the first yellow card of the game following a foul on the half way line.
With 28 minutes played, Scunthorpe took the lead as they turned defence to attack following a free-kick to Vale. Howard unleashed Eisa down the left, who brought the ball forward, with the winger then curling a long range effort across goal and into the corner of the net for his first goal of the season.
Soon after, Loft strode forward and sensed the loose ball, winning possession on the right channel before he teed up for Spence, whose cross was blocked for a throw.
With 33 minutes on the clock, Loft and Brown both went up for the ball following Rowe’s cross into the area. The Vale ‘keeper ended up on the deck, but neither player touched the ball.
There was then a big penalty shout as Kevin van Veen controlled the ball inside the area and was hauled down. The referee waved away the protests from the Iron, however.
The last action of note from the opening half saw Eisa almost get in inside the box, but Smith defended well and brought the ball clear for the hosts.
There was an early second half chance for the hosts as Cullen had a go from 25-yards with the effort going over the bar.
Alex Gilliead then controlled a cross into the area and brought the ball away and over the half way line. He looked to slip in Loft, but the ball was gathered by the home ‘keeper.
At the other end, Conlon then had a go from range, but he cut across the ball and the effort flew wide.
With 52 minutes gone, Worrall and van Veen clashed on the half-way line, with the Dutchman staying down. He received treatment before being soon replaced by John McAtee.
In the 56th minute, Rowe headed away following a cross from the left side. The hosts won the ball back with another cross coming in from the left, but the Iron defended really well inside their six-yard box.
A minute later, Loft hit the post after he was threaded in down the right and shrugged off his man before advancing on goal. His drive across goal rattled back into play for the home goalkeeper to gather.
The 61st minute saw good Iron defending as Worrall chested down and volleyed an effort towards goal, with a block put in allowing the ball to spin towards Howard for him to gather.
Eisa then rolled his man and looked to advance on goal, but for a brilliant last ditch tackle. At the other end, a cross came in which Brown chested down and clears.
Soon after, Harry McKirdy slotted an effort wide from 20-yards after cutting inside.
The hosts had their best chance of the night so far with 67 minutes gone as Cristian Montano received the ball on the left side of the box from Devante Rodney, he played a cross in for Cullen, but it just evaded him and United could breath a sigh of relief.
With 72 minutes gone, McGahey headed clear a goal-bound effort as the hosts played the ball inside the penalty area. They then won a free-kick on the edge of the area which Conlon took, and saw deflected over the bar. Nothing came from the subsequent corner.
Three minutes later, Loft was replaced by Devarn Green as United made their second change of the night.
United continued to defend resolutely as the hosts probed for a leveller but couldn't create anything clear cut.
There was a final Iron change with four minutes remaining as Bedeau replaced Eisa to re-enforce the defence in the closing stages.
On 88 minutes, Rodney put in an inviting cross from the right for the hosts which flashed across the box, but out of play for a goal kick.
A minute later, there were shouts of handball as Onariase blocked a goal-bound effort with his face but the referee wasn't having it, and United got it clear.
There was drama during the second minute out of four in stoppage time as the hosts thought they'd scrambled the ball over the line from close range, but Howard stopped it and the referee blew for a free-kick as he judged the Iron goalkeeper to have been fouled.
Scunthorpe return to action on Saturday when they host Morecambe in Sky Bet League Two (3pm kick-off).
PORT VALE: Brown, Clark, Smith, Legge, Crookes (Montano, 52), Oyeleke, Conlon, Burgess (McKirdy, 63), Worrall, Amoo (Rodney, 65), Cullen.
PORT VALE SUBS NOT USED: Visser, Brisley, Fitzpatrick, Pope.
IRON: Howard, McGahey, Onariase, Gilliead, Loft (Green, 75), van Veen (McAtee, 54), Eisa (Bedeau, 86), Brown, Spence, Beestin, Rowe.
IRON SUBS NOT USED: Watson, Hippolyte, Hallam, Dünnwald-Turan.