Warnock saw his latest side snatch a last-gasp win from the stands at Elland Road last week, but will be disappointed Leeds failed to convert one of several chances.
Leeds striker Ross McCormack came closest to breaking the deadlock when his shot hit the bar and bounced down on to the goalline early in the second half.
Robert Snodgrass headed home the rebound, but his follow-up effort was ruled out for offside.
The point gained is of little use to either side. Leeds remain four points adrift of the play-offs and Portsmouth, who dropped into the bottom three after being docked 10 points for going into administration, slipped another place courtesy of Coventry's win over Barnsley.
Pompey manager Michael Appleton, forced to sell top goalscorer Erik Huseklepp to Birmingham this week, once again struggled to fill his substitutes' bench and handed a debut to 21-year-old midfielder Scott Allan, who joined on loan from West Brom on Thursday.
Defender Greg Halford returned to the side, while striker Dave Kitson was suspended.
Michael Brown was back in Leeds' starting line-up in place of the departing Andros Townsend, while Warnock handed the captain's armband to Snodgrass.
Leeds were dealt an early blow when defender Alex Bruce was forced off injured in the 11th minute and replaced by Leigh Bromby.
Goalkeeper Andy Lonergan tipped away Portsmouth midfielder George Thorne's corner soon after, while Adam Clayton drove the wrong side of the post for Leeds.
Allan almost made a dream start when his long-range shot flashed wide and Pompey team-mate Hayden Mullins' angled effort was blocked.
Both sides were finding it difficult to carve out clear-cut chances.
Pompey defender Tal Ben-Haim tried his luck with a wayward 30-yard shot before Leeds came closest to breaking the deadlock just before half-time when Snodgrass's shot from a half-cleared corner was brilliantly saved by Stephen Henderson.
Leeds almost took the lead with their first meaningful attack in the second half.
McCormack's thumping drive from the left edge of the penalty area hit the crossbar and bounced down on the goalline and although Snodgrass followed up to head home, the Scot was deemed to have been in an offside position by referee Phil Gibbs.
Pompey pair Ward and Mullins fired in long-range efforts that were blocked and comfortably saved respectively before Henderson rescued his side again, this time saving with his feet to deny Luciano Becchio inside the penalty area in the 58th minute.
Henderson saved with his feet again to keep out Bromby's close-range shot, but just as Leeds began to dominate, Thorne unleashed a 20-yard shot that forced Lonergan into a fine save.
Aidy White almost caught Henderson out with a cross-shot that was tipped over, fellow Leeds defender Darren O'Dea headed straight at Henderson in the closing stages and Brown lashed a shot over the bar in the 94th minute.