Gus Poyet's side came into the game having won just three of their last 17 games, but went ahead when Dean Hammond, restored to the first XI, nodded in a 15th-minute opener.
Craig Mackail-Smith's 11th goal of the season doubled the lead, before a stunning long-range effort from Wayne Bridge secured all three points.
After five wins from their last seven games, Blues boss Mick McCarthy was hoping to name an unchanged team for the fifth successive game.
But Andy Drury's illness forced McCarthy into making one alteration to his side, with midfielder Nigel Reo-Coker restored to the starting line-up as replacement.
Young defender Tyrone Mings was named among the substitutes for the first time, after signing from Chippenham last month.
Poyet made two changes to his team, with Ashley Barnes and Hammond coming in for Andrew Crofts and Bruno.
It was Hammond who broke the deadlock, as the Southampton loanee headed home Andrea Orlandi's inswinging near-post corner to put the away side ahead.
Polish goalkeeper Tomasz Kuszczak, making his 100th English league appearance, then needed to be alert to maintain the advantage as he denied Daryl Murphy's goalbound effort with an outstretched save.
Barnes' flick on presented Mackail-Smith with the opportunity to double the Seagulls' lead after 34 minutes.
The Albion top scorer made no mistake, edging past Aaron Creswell before sending an arrowed effort in off the inside of the post.
The hosts were unbeaten at Portman Road under McCarthy, but struggled to build any momentum against Poyet's men.
Their frustrations were exemplified by Lee Martin's ambitious effort from distance moments before half-time which flew high and wide.
McCarthy's side pressed for a route back into the game after the interval, but found clear-cut opportunities hard to come by.
Guirane N'Daw came closest to giving the home side hope, but his speculative effort failed to hit the target after 53 minutes.
McCarthy made a double switch midway through the second half to try and engineer a comeback with Michael Chopra and Jason Scotland coming on for Murphy and leading marksman DJ Campbell, who was making the last appearance of his loan spell before returning to parent club QPR.
The substitutions failed to have the desired effect, as Poyet's men wrapped up the victory moments later.
Gary Dicker's pass picked out Bridge who unleashed a superb strike from distance which rocketed past a helpless Stephen Henderson.
The Tractor Boys were unable to open up their opponents, with their final sight of goal falling to Martin whose curling effort failed to test Kuszczak late on.
- Sports & Recreation
- Gus Poyet
- Dean Hammond
- Wayne Bridge