Danny Haynes' fortuitous strike on the stroke of half-time settled an entertaining encounter at Selhurst Park between two sides separated only by goal difference at the start of the match.
Haynes knew little about his decisive touch with just seconds to go in the first period.
The striker, who was only on the pitch after Alan Quinn picked up an injury in the warm-up, was in the right place at the right time as Richard Naylor's wayward volley struck his head and deflected into the back of the net.
It was rough justice on a Palace side who had picked up 16 points from a possible 21 under Warnock at home, but they have now lost back-to-back Championship matches and on such margins promotion to the top-flight is often decided.
Warnock had recalled left back Lee Hills and winger Sean Scannell to the starting line-up, but he side were second best in the early stages.
Goalkeeper Julian Speroni was called into action for the first time on 20 minutes when he palmed an Alan Lee header behind for a corner.
From the resultant flag-kick, Hills justified his selection by clearing a goalbound header off the line.
Hills also had an impact at the other end when his low cross found its way to Scannell, but the teenager's shot was blocked by some frantic Ipswich defending.
The Eagles were growing in confidence and Ben Watson should have done better than drill a left-foot shot straight at visiting goalkeeper Stephen Bywater after a delightful Scannell back-heel.
Mark Hudson was next to try his luck after latching onto a long Matt Lawrence ball, but he pulled his shot badly wide of the mark in the 38th minute.
Palace continued to take the game to the visitors in the second period and the pressure kept Town on the back-foot and relying on counter-attacks to extend their lead.
However, they were thankful the referee decided to show Speroni only a yellow card for bringing down Jon Walters just outside the area early in the second period.
Warnock sent on Dougie Freedman, Shefki Kuqi and Carl Fletcher in a bid to force the issue, but Ipswich produced a strong rearguard action to keep the home side at bay.
Haynes drew a 73rd minute save out of Speroni with a low shot in a rare moment of danger in the home box.
The Eagles best chance for a point came via Clinton Morrison in the 79th minute following a pinpoint Danny Butterfield pass.
The in-form striker snatched at a volley in the penalty area and watched in agony as the ball whistled the wrong side of the post.