David McGoldrick gave Blues an early lead but Leeds left Portman Road with all three points for the first time in 11 years.
Town could have been in total control at the break after the summer signing from Nottingham Forest had beaten Paddy Kenny with a 20 yard drive but Luke Varney levelled the scores after the ball fell kindly for him from a deflection.
Ross McCormack’s 48th minute goal won it for the Whites, his shot from distance evading Scott Loach low down.
Mick McCarthy stayed with the same side that were within a couple of minutes of taking a point at QPR last weekend, Dean Gerken the only change to the 18, the ‘keeper recovering from a dead leg to take his place on the bench.
Blues started brightly and Jay Tabb had the first effort at goal, Paddy Kenny making a comfortable save.
The midfielder had the ball in the net soon after, a terrific cross by Aaron Cresswell – one of many during the opening half hour, fell to McGoldrick who forced it goalwards and Tabb got the final touch only to see the offside flag raised.
Blues had better fortune on 11 minutes though - no luck needed as McGoldrick cut inside Tom Lees and smashed a low drive past Kenny into the bottom corner.
Leeds responded with Jason Pearce volleying over from a corner, Varney then almost getting on the end of McCormack’s cross.
At the other end, Lees deflected a Carlos Edwards corner over the bar, McGoldrick showing great skill to create space, his slick pass almost finding Daryl Murphy.
Cresswell hit the woodwork with a strike from 25 yards, Tabb sent the rebound into the sidenetting as Blues pressed for a second but it was Leeds who struck next, McCormack’s shot deflected by Luke Chambers into Varney’s path and his left foot finish gave Loach no chance.
McGoldrick tested Kenny with a left foot strike but it was a misunderstanding at the back between the Leeds’ ‘keeper and team-mate Pearce that presented Town with the best chance of adding to the scoring before the break but Murphy couldn’t force the ball home with the goal gaping.
Three minutes into the second-half Leeds were in front, McCormack’s 30 yarder sliding under Loach.
Luke Hyam’s spectacular diving header went wide as Blues looked to respond, Cresswell’s free-kick – after he had been clattered by Austin, the Leeds’ skipper yellow carded for the challenge, then hacked clear.
A terrific pass from Skuse released Elliott Hewitt inside the Leeds’ box but Town couldn’t captitalise on the cross before Blues made a double change just past the hour, Paul Anderson and Ryan Tunnicliffe on for Edwards and Tabb.
Anderson was immediately in the action, swinging in a corner that Murphy met with his head, Noel Hunt in the right place to clear off the line.
Town made a third change for the last 15 minutes, Frank Nouble on for Murphy, while Varney made way for Dominic Poleon.
Loach beat out a Hunt effort after good interplay from the visitors, then Paul Green was inches away from finding the target.
Hyam was equally close at the other end with a 20 yarder, Tunnicliffe’s strike headed out by Pearce as Leeds stood firm to see out a first win at Portman Road since 2002.
Town: Loach, Hewitt, Chambers, Smith, Cresswell, Edwards (Anderson 65), Skuse, Hyam, Tabb (Tunnicliffe 65), Murphy (Nouble 75), McGoldrick. Subs: Gerken, Berra, Veseli, Taylor.
Leeds: Kenny, Peltier, Pearce, Lees, Warnock, Green, Murphy, Austin, McCormack, Hunt (Tonge 83), Varney (Poleon 75). Subs: Ashdown, Drury, Smith, Diouf, Wootton. Booked: Austin.