Former Liverpool ace Patrik Berger scored the only goal of the game to earn Portsmouth their first win in four league matches.
The Czech international, who was discarded by Liverpool manager Gerard Houllier in the summer after making only one league appearance last season, scored on three minutes to condemn the visitors to their third successive league defeat.
The visitors nearly took the lead on 90 seconds when right-back Steve Finnan's hopeful throughball found England striker Emile Heskey in the Portsmouth box.
The busting striker held off defender Arjan De Zeeuw only to see his right-foot shot come back off the post and cleared to safety.
The home side took the lead on three minutes through Berger after he poked home defender Sebastien Schemmel's right-wing cross.
Australian international Harry Kewell hit a free kick straight at Shaka Hislop on six minutes as the visiting side failed to create any telling chances in the first half.
Portsmouth nearly doubled their lead on 38 minutes when veteran striker Teddy Sheringham flicked on for strike partner Yakubu Ayegbeni. The pacy striker showed neat control but was unfortunate as his hooked shot went just wide of the left post.
Ten minutes into the second half Heskey turned inside defender Boris Zivkovic only to see his goalbound effort plucked out of the air by keeper Hislop.
The hosts almost added a calamitous second on 63 minutes when Liverpool midfielder Igor Biscan attempted to clear a free kick.
Schemmel's inswinging cross struck Biscan's head and the ball came crashing back off the right-hand post to save his blushes.
With three minutes left the lively Ayegbeni saw his spectacular effort from 25 yards come crashing off the underside of the bar and to safety.
Seconds later, Liverpool should have levelled when substitute Florent Sinama Pongolle found himself well placed eight yards out only to see his weak effort go wide.
Moments later, the French striker again dragged his shot wide this time from three yards out after Portsmouth failed to clear a Kewell cross.