Scunthorpe started life after Brian Laws with a hard-fought 2-1 victory at Portsmouth.
The hosts went ahead through Tom Craddock but a close range double from David Syers sealed an important away win for caretaker manager Russ Wilcox and Tony Daws' men.
It was a victory that took United up four places to eighth in League Two - sitting out of the play-off zone on goal difference.
The Iron entered the game making two changes from the team beaten by Grimsby Town in midweek, with Dave Syers and Reuben Noble-Lazarus in for Michael Collins and Jimmy Spencer.
Collins was rested after playing three full games in quick succession following his return from injury.
The Iron, wearing their orange away kit, started brightly and tried to force the foothold as they looked to provide a positive reaction following Laws' exit as manager in midweek.
After a couple of close shaves at either end, Scunthorpe had the first shot on goal in the sixth minute when Deon Burton's snapshot from 30 yards went wide of the post.
He then tried another attempt, on the turn, against his former club four minutes later but the ball drifted just wide.
Then Sam Winnall sent one wide after being played through by Reuben Noble-Lazarus. He placed it agonisingly to the wrong side of the post from 15 yards.
As the half wore on, the hosts tried to come more into it but Scunthorpe succeeded in frustrating Pompey and their fans.
On 30 minutes, Trevor Carson was drawn into a great stop as he tipped wide an effort from Sean McAllister, who tried to curl into the top corner from long range.
Then, just three minutes later, they came close again as another shot from distance - this time Winnall from 25 yards - drifted just wide of Carson's bottom right-hand post.
The hosts took the lead on 36 minutes as Craddock guided home a header from close range following aright-wing break and subsequent cross, which found the former Luton man.
United levelled just four minutes later though as Andy Dawson lofted over a right-wing corner which Niall Canavan guided towards the line, and Syers smashed in from close range for his first goal for the club.
Straight into the second half, Burton was presented with a chance - being positioned one-on-one with the goalkeeper on the edge of the box following a McAllister pass but his low drive was blocked away to safety.
Then, on 48 minutes, Winnall drew a palmed save from Carson - creating a shooting opportunity out of nothing before seeing his attempt saved.
Portsmouth then quickly broke and Barcham almost found the net, only for McAllister to come in with a last ditch tackle and block it with some terrific defending.
Burton then had another chance to notch for the Iron, firing at thin air after the ball had been flicked on to him by David Mirfin following a corner.
Ricky Holmes came close for the hosts on 54 minutes, hitting the crossbar. He took the corner and received it back, looping a shot towards goal which clipped the top of the woodwork.
Slocombe was then drawn into a world class save four minutes later as the ball came in for Johnny Ertl, whose header looked a certain goal - however it was clawed away by the Scunthorpe 'stopper.
There was a United change on 64 minutes as Noble-Lazarus was replaced by Adelakun and he steamed into action straight away, receiving the ball from the left and drilling a low shot towards goal, which Carson stooped low to stop.
Six minutes later, they took the lead. After dealing with some Pompey pressure, they broke and Winnall cut inside from the left before seeing his low shot spilled by Carson, into the path of Syers who bundled home his second from close range.
Scunthorpe tried to keep up the pressure as they seeked a third goal. Carson was drawn into a great save as Burton laid off the ball for Winnall who hit it on the volley, with the home 'stopper tipping the ball onto the post.
Then, from the resultant corner, Adelakun's long range shot was tipped away for another corner.
On 77 minutes, Syers had the chance of a hat-trick as he saw his volley from 20 yards tipped away for a corner.
Adelakun then dragged a shot wide from 30 yards after the ball had been punched out by Carson from the subsequent set-piece.
The visitors made another substitution with a few minutes left as Burton was replaced by Eddie Nolan, back in first team action for the first time in two months after a hamstring injury.
United were successfully managing to shut out the home side and, with two minutes remaining, Winnall was next to come close - clipping the ball as he drive across the goalkeeper from an acute angle from the left side of the area.
There were four minutes of stoppage time and, two minutes into those, Luke Waterfall came on for Hawkridge as Scunthorpe switched to five at the back and successfully saw the win out.
Scunthorpe are next in action on Tuesday when they visit Rochdale (7.45pm kick-off).
Portsmouth: Carson, N'Gala, Devera (East, 78), Bradley, Barcham, Craddock, Holmes (Bird, 86), Ertl (Connolly, 73), Ferry, Potts, Wallace.
Substitutes not used: Sullivan, Moutaouakil, Painter, Cooper.
Scunthorpe United: Slocombe, Ribeiro, Mirfin, Canavan, Dawson, Hawkridge (Waterfall, 90), Syers, McAllister, Noble-Lazarus (Adelakun, 64), Burton (Nolan, 86), Winnall.
Substitutes not used: Severn, Iwelumo, Byrne, Spencer.