Scunthorpe's opener sparked the Seasiders into life and they notched four goals in reply, aided by the sending-off of visiting keeper Joe Murphy.
In contrast the first 45 minutes were a drab affair with the visitors' five-man defence shackling an unimpressive home side.
Blackpool edged the first half, their best chance coming on the 11th minute when Billy Clarke breached the visitors' defence only to see his looping shot come back off the post.
The Iron made few attacks in a scrappy 45 minutes and Blackpool seemed a team out of sorts with the fluid passing and constant attacks of recent games replaced by disjointed play.
The Iron opened the scoring against the run of play on 51 minutes when Paul Hayes beat the offside trap and neatly chipped the ball over stranded keeper Matt Gilks.
Scunthorpe's lead lasted just eight minutes as Blackpool fired into life. Playmaker Charlie Adam's free-kick reached Alex Baptiste and his superb cross was headed home by Ian Evatt.
Two minutes later the visitors were down to ten men. Keeper Murphy came out to collect a cross and the ball fell to Hameur Bouazza.
Murphy instinctively put his hand up to save the goal bound shot but was yards outside the area and received his marching orders.
Adam put the Seasiders ahead with a ferocious free-kick that replacement keeper Sam Slocombe had no chance of saving.
A rampant Blackpool side tore into the visitors and seconds later Keith Southern smashed the ball against the underside of the bar.
Scunthorpe's Slocombe then gifted the Seasiders their third spilling Stephen Crainey's low cross to give striker Ben Burgess an easy tap-in.
The Seasiders pressed on and a minute before time Baptiste got on the scoresheet with a thundering 25-yard drive.
Scunthorpe never gave up with a battling display and Matt Sparrow was unfortunate to have a goal disallowed deep into extra-time.