On-loan Stoke midfielder Tom Soares drove a 20-yard shot into the top corner in the 71st minute and substitute Leon Clarke added a late second to give Irvine his second win inside four days and leave Blackpool stunned.
Charlie's Adam injury-time strike was little consolation for Blackpool but Irvine has breathed new life into Wednesday and their new-found resolve was evident throughout at a bitterly cold Bloomfield Road.
Irvine, who began his reign with a 2-1 win at Barnsley last Saturday, said: "It's a fantastic start and the lads deserve enormous credit for the way they've gone about things.
"What has been the difference? I don't know.
"It could quite simply be a change of voice and a new face, but the lads have certainly taken a lot of things we have talked about on board.
"But it's early days and this could just be the honeymoon period.
"Having said that, I think Blackpool are a very good team so I'm absolutely delighted."
Eyebrows were raised when Irvine, 51, was shown the door at Preston earlier this month but he wasted no time in getting back into work and has rapidly stamped his mark on the underachieving Owls.
The result prevented Blackpool from climbing into the top six but should pour confidence into Irvine's team as they brace themselves for the tests that lie ahead.
Irvine, whose side lost winger Jermaine Johnson to a hamstring injury in the first half, added: "I've lost count of the number of people who have said they were shocked by Preston's decision to let me go.
"I was myself, obviously, but at the end of the day these things happen. I know my own views on the matter, but I'm biased!
"We've had two fantastic away results but we've got to make sure we continue it at home now and win enough games to stay in this division."
A biting, swirling wind hardly encouraged freeflowing football but Wednesday dug deep to defend admirably and hit Blackpool with two late sucker punches.
Blackpool boss Ian Holloway, whose side would have climbed into the play-off places had they won, felt they lacked energy.
He said: "That was nothing like we've been playing.
"People have got carried away and saying we could do this and we could do that.
"We're not ready for that yet - the people that I put in the team tonight lost a bit of energy and I don't think people believed in them.
"I've just had a bit of a pop because we all have to believe ourselves first and foremost and sometimes tell each other the honest truth.
"I think David Vaughan needed to be told because that wasn't him tonight."
Source: Team Talk