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 npower 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.
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 Jimmy Bullard and Ronan Murray.
Source: PA
Source: PA