Preston meanwhile slumped to a sixth defeat in a row and Craig Brown's patched up team rarely threatened once Marcus Bent had put the hosts ahead.
Pablo Counago twice fired over early on for Town before Marlon Broomes cleared away a wicked low cross from Fabian Wilnis close to his own line.
David Healy shot wide for Preston before Town went ahead on the half hour, Marcus Bent glancing home Jim Magilton's free-kick.
The goal fired up Ipswich and Jonathan Gould did well to turn a Counago shot aside, before Tommy Miller fired just wide.
In first-half stoppage time, Counago’s run ended with the ball dropping to Magilton, whose chip sailed just wide.
Despite being outplayed in the first half, Preston had a great chance to equalise five minutes after the break.
A deep cross by Lee Cartwright was headed back by Colin Murdock for Pawel Abbott who looked sure to score before Thomas Gaardsoe’s last-ditch block.
Town had most of the pressure but only made the game safe in the 73rd minute when two of their subs combined.
Darren Ambrose, with his first kick, whipped in a corner which Hermann Hreidarsson flicked on for Darren Bent to bundle in at the far post, with Preston appealing in vain for handball.
Darren Bent had a volley well held by Gould before he got his second of the game and tenth of the season four minutes from time.
Ambrose was again the provider with a ball over the top and Bent outpaced Broomes before coolly slotting beyond Gould.
It concluded a routine win for an Ipswich side mounting a strong play-off challenge while Preston, missing 13 players, continue to slide down the table.