Scottish striker Iwelumo, who cost just £400,000 from Charlton earlier this summer, had struck twice in the midweek Carling Cup win against Accrington Stanley.
That earned him his first Championship start against Wednesday and he didn't disappointment with a classy performance.
It was an impressive victory for Wolves, who had fallen behind after just 15 minutes through Etienne Esajas.
But that was as good as it got for Wednesday, who were unable to repeat the attacking heroics they showed when they beat Burnley 4-1 in their opening game of the season.
Iwelumo headed Wolves level in the 28th minute, a Sylvan Ebanks-Blake penalty put them in control before Iwelumo struck again with David Edwards completing the rout in stoppage time.
The opener from Esajas was somewhat against the run of play as Wolves had twice threatened to take an early lead only for goalkeeper Lee Grant to deny Matt Jarvis and Richard Stearman with smart saves.
Wolves were then stunned when a long through ball from Mark Beevers picked out Deon Burton on the edge of the area.
Burton fed Esajas who breezed past left-back George Elokobi before beating Wayne Hennessey with a low near post drive.
Despite the shock of falling behind, Wolves continued to look the more potent side and they were rewarded when Iwelumo continued his rich vein of form.
Wolves' right-back Kevin Foley whipped in a pin-point cross that was powerfully headed home by Iwelumo from 10 yards.
They would have gone on to take a lead into half-time had Grant not again come to the rescue of Wednesday by tipping Michael Kightly's rising drive over the bar.
But they only had to wait eight minutes into the second half to move in front when Ebanks-Blake converted from the spot after Jarvis was fouled by Sean McAllister.
Iwelumo then ended Wednesday's challenge in the 59th minute - tapping in from close range when he latched on to the rebound after Kightly had hit the post from close range.
Edwards gave the final scoreline a comprehensive look in the first minute of stoppage time when he collected a flick from Ebanks-Blake before beating Grant from 16 yards.