He was a constant threat to the visitors defence and capped a fine performance when playing an effective one-two with Ishmel Demontagnac, before sliding the ball home from close range in the 89th minute.
Until that time it had never been certain that Walsall would win despite having the one-man advantage.
The Iron made a dream start when clever work down the left by Kevan Hurst enabled him to cross to the far post for Garry Thompson to outjump Paul Boertien and head the opening goal.
Scunthorpe were looking the more skilful side, but suffered an irreversible blow in the 10th minute when central defender David Mirfin, making his debut, was rightly sent off for a foul on Ibehre who had a clearer goalscoring chance.
And there was worse to come as, direct from the free-kick, Walsall's German midfielder, Marco Reich, sent a stunning drive past helpless keeper Josh Lillis.
Although the Saddlers had most of the play after that, they didn't pose any real threat to a visitors' defence in which skipper Izzy Iriekpen was outstanding.
Ibehre broke clear in the 25th minute from a pass from Stephen Hughes but drove an angled shot well off-target.
Five minutes after the interval Scunthorpe defender Cliff Byrne almost turned the ball into his own net from a dangerous cross by Alex Nicholls and, from the resultant corner, Richard Taundry had a header saved by Lillis.
Ibehre continued to be dangerous and in the 62nd minute he flicked the ball on from a cross by Taundry, only for Sofiane Zaaboub to shoot over.
Ibehre tested Lillis with a shot on the turn in the 70 minute and, two minutes later, blotted his copybook when sending a free header straight at the keeper from a cross by Palmer.
When the winning goal came there was a booking for Scunthorpe defender Marcus Williams, who had claimed strongly to a linesman that Ibehre was offside, but the goal stood and Walsall claimed a somewhat fortunate victory.