The home side had the majority of possession but could not find a second after the second-half equaliser.
135 Yeovil fans made the long trip to North Lincolnshire and they were celebrating within half an hour of kick-off, as Joel Grant put them into the lead after a quick counter attack.
Paddy Madden had the chance to level United from the spot against his old team, but his effort was saved before the interval. It was the 18-year-old who found the back of the net shortly after coming on to replace Tom Hopper after a mazy run on the right-hand side.
The Iron entered the game against Yeovil Town looking to make it three wins from their last four home matches and Mark Robins made four changes from the side that lost to Barnsley on Tuesday.
Alex Davey came into the side to partner Niall Canavan in defence in place of Andrew Boyce, who dropped to the bench.
21-year-old defender Conor Townsend joined the Iron on a one-month loan hours before kick-off and he started at left-back in place of Marcus Williams, who picked up an injury in midweek.
With Neal Bishop serving a suspension after accumulating ten yellow cards this season, George Evans replaced him in midfield. Gary McSheffrey was the stand-in captain and took Kevin van Veen’s place in a front three.
It was a quiet opening quarter of an hour, with few chances to note until George Evans had the best chance from a central position, with a 25-yard drive which went just past the post.
There was a hopeful penalty appeal as McSheffrey came inside from the left and was felled in the box, but the referee indicated that the Yeovil man had got the ball, shortly before Madden sent a glancing header past the post as United grew into the game.
Then, against the run of play, the visitors took the lead after 29 minutes, when Gozie Ugwu broke free on Yeovil’s left-hand side. He shot at Iron goalkeeper Luke Daniels, who made himself big and saved well. The former West Brom stopper parryied the shot and Grant followed it up from close range to give the Glovers the lead.
Alex Davey’s raking long-field pass found McSheffrey, who sent in a fine cross and goalkeeper Artur Krysiak beat Hopper to the ball. It came out to Madden and the Irishman sliced his shot wide. There was a pause in play as Krysiak took a blow in the process and had to be substituted.
United pressed for an equaliser before the break as a quick move saw McSheffrey sprint to byline and drive the ball across goal, but Yeovil cleared, followed by another cross by the captain, this time Madden could not find the target with his header.
Six minutes of added time was played after the injury to Krysiak and, as the whistle loomed, Madden was hauled down in the six-yard box and a penalty was awarded. The Irishman stepped up against his former club and substitute Gareth Stewart dived the right way, saving excellently as the Glovers led at the interval.
Early in the second half there was a nasty clash of heads between Clarke and Yeovil’s Nathan Smith, which meant more stoppages. After treatment, both players continued, with Smith sporting a bandage.
Robins made his first change while play was stopped, swapping Hopper for Adelakun and the young winger made a positive impact. He sent a couple of crosses in from the right before a moment of trickery saw him dribble inside and send a low strike across goal and into the bottom corner.
The leveller gave Glanford Park a lift, as the home support rallied behind their men to push for a second.
The lively Adelakun, clearly full of confidence after his goal - which was his third of the campaign - made a dangerous run past his man in the box, but he mishit his shot.
United came close when Evans took a deep free-kick to the far post and Davey headed it across goal to Madden, who was a fraction offside.
After soaking up pressure for the opening 30 of the second half, the Glovers nearly took another fortunate lead after good work from Liam Shephard, who crossed and found Stephen Arthurworrey at the far side. From the edge of the six-yard box, he dragged his shot across goal and past the post.
United again asserted their dominance as Madden went close again before McSheffrey’s successive whipped balls across the area went unattacked.
Clarke nearly got his first Scunthorpe goal as his close-range shot was saved by Stewart before McSheffrey’s dink nearly beat the visiting goalkeeper. The former Coventry City defender was soon at the other end to make a last-ditch challenge to prevent Yeovil.
Another six minutes were added on at Glanford Park and Isaiah Osbourne went close with a powerful cross, but United could not muster a winner as they shared the spoils with the Glovers.
Scunthorpe United: Daniels, Clarke, Davey, Canavan, Townsend, O'Neil, Evans (McAllister, 90+3), Osbourne, Madden, McSheffrey (van Veen, 84), Hopper (Adelakun, 55).
Substitutes not used: Anyon, Boyce, Wootton, Llera.
Yeovil Town: Krysiak (Stewart, 36), Smith, Foley, Moore (Hayter, 79), Grant (Berrett, 69), Ugwu, Arthurworrey, Webster, Sheehan, Shephard, Kingsley.
Substitutes not used: Twumasi, Davis, Eastmond, Morgan.
Attendance: 3,783 (135 away).