First-half goals from Jason Scotland and David Norris put the Tractor Boys in control at the break and although Paul Coutts hit back early in the second half, Preston's comeback never materialised.
Having conceded nine goals in their previous two matches, including five against fierce rivals Norwich in their previous home match, Paul Jewell's side will have been pleased to mark the occasion of their final home Championship game of the season with a win.
North End's recent good record at Portman Road, where they had won on three of their previous five visits, seemed to count for little as they toiled in the Suffolk sunshine throughout the first half.
The defence was caught napping inside the opening 10 minutes when Josh Carson burst into the area and squared the ball for Scotland, who made no mistake from 12 yards.
The hosts pressed again soon after but Jimmy Bullard's searching diagonal ball was just too long for Norris.
And in the 19th minute the hosts doubled their advantage when Norris powered home his 11th of the season from inside the box after good work from Bullard and Ronan Murray.
A shell-shocked Preston side tried to pick themselves up from the double blow and won a succession of corners, but Danny Mayor's deliveries failed to create a clear opening.
North End boss Phil Brown made an early change as he sought to reinvigorate his flagging side, with Keith Treacy coming on for Jamie Proctor.
But Billy Jones' miscued effort from the edge of the area, which was gathered and cleared easily by Bullard, summed up their first-half display.
The match came to life as a contest seven minutes into the second half when Coutts directed a neat effort into the bottom corner from 18 yards out.
The goal unsettled Ipswich as the away side began to cause them more problems. Marton Fulop fumbled a shot from Coutts and Mark Kennedy had to clear under pressure as Brown's men went in search of an equaliser.
Ipswich were beginning to lose their shape and discipline, allowing the likes of Coutts, Adam Barton and Barry Nicholson to pull the strings in midfield.
Fulop was forced into a smart save when Nicholson latched onto Barton's through-ball as North End stepped up the pressure.
An increasingly restless home crowd were almost relieved of their frustrations when Bullard found himself with a chance to shoot from 20 yards, but his usually reliable right foot let him down as he blasted over.
With time running out, Coutts fired one last chance narrowly wide but Ipswich held on to give themselves a shot of finishing in the top half, while Preston will need a win on the final day to avoid finishing bottom of the pile.