Two goals in three first-half minutes sealed a crucial win for the hosts against plucky ten-man Reading, whose own play-off chances suffered a potentially crippling blow.
Gareth McAuley and Jon Walters found the back of the net just before the interval, after Matt Mills' contentious sending off, and the visitors could only reply with Gylfi Sigurdsson's 90th minute free-kick.
Reading started the brighter and Ipswich hardly got out of their own half for the first 15 minutes, but the hosts were the first to threaten when Daryl Murphy pulled back from the byline and David Healy's angled shot was pushed away by Adam Federici.
David Norris was booked for a dive after tangling with Zurab Khizanishvili before Walters' downward header found Healy, whose overhead kick was palmed away by Federici.
Brian Murphy in the Ipswich goal parried a Jobi McAnuff snap-shot from 20-yards before Federici dived to hold Healy's curling effort, but the game changed on the half-hour when Mills harshly saw red.
The defender and Norris both slid in for a 50-50 challenge with studs showing, but Norris got there slightly ahead and Mills caught him with referee Keith Stroud deciding it was worthy of a red card.
Federici saved from Daryl Murphy and Grant Leadbitter either side of McAnuff blazing over from an angle, but Ipswich grabbed the lead on 41 minutes when McAuley's firm header from Leadbitter's corner beat Federici and a defender on the line.
Town doubled their lead on 44 minutes when David Wright's cross to the far post was helped back into the centre by Daryl Murphy for Walters to beat sub Alex Pearce and Khizanishvili to nod home.
If home fans thought their side would go on to win comfortably they were in for a rude awakening as Reading dominated the early stages of the second half, with Jimmy Kebe shooting over, Shane Long nodding over from McAnuff's cross and both Sigurdsson and Brian Howard firing fierce drives just over the bar.
Ipswich finally perked up and began to move the ball about to take advantage of their extra man as Murphy shot wide.
Youngster Connor Wickham came of the bench to head home, but his header was correctly ruled out for offside.
Jack Colback then found Wright raiding forward and he cut inside his man but his curling shot was easily claimed by Federici before Kebe's angled shot at the other end was deflected just wide.
Wickham then surged forward onto a throw by 'keeper Brian Murphy before flashing a shot wide and a neat Town passing move ended with a firm 20-yard drive from Leadbitter being held by Federici.
Sub Pablo Counago played in Colback for a great chance to clinch it for Town, but Federici blocked his first effort and then the on-loan Sunderland winger blazed the rebound over.
Hal Robson-Kanu came on to drive narrowly wide following a lay-off from fellow replacement Simon Church and Church then came within inches of reaching Kebe's teasing cross right in front of goal.
In the final minute, Sigurdsson curled home a 22-yard free-kick to give Reading hope, but Town held on comfortably enough, and could have increased the lead but for a good save by Federici from Counago's volley.