Richard Hughes scored his first goal for Portsmouth but it was goalkeeper Shaka Hislop who propelled Portsmouth into an FA Cup quarter-final clash with Arsenal at Fratton Park.
Hughes scored the only goal of the game in the 72nd minute drilling a 12-yard left-foot shot wide of the diving Chris Kirkland.
Hughes, a former Arsenal apprentice, had not scored in his previous 18 months as a Pompey player after arriving from Bournemouth for Â£50,000.
Hislop capped a magnificent afternoon with a penalty save from Michael Owen after 61 minutes.
Matt Taylor clipped the heels of Milan Baros but Hislop had no trouble saving Owen's weakly struck spot-kick.
Hislop saved Pompey when he blocked a shot from Emile Heskey with his legs in the 37th minute and his heroics continued after the break.
Almost immediately after the goal from Hughes, Hislop was perfectly placed to tip over a fierce header from Steven Gerrard.
Pompey had an escape in the 49th minute when referee Matt Messias awarded a penalty for handball but, after consulting his assistant, decided the handball had been by a Liverpool player, Baros, and changed his decision.
Portsmouth lived dangerously and Arjan De Zeeuw almost turned the ball into his own net but for Liverpool it was a question of failing to make the best use of their dominance and their chances.
Portsmouth had Nigel Quashie, Hughes, busy Russian Alexei Smertin and Yakubu booked as they fought desperately for control.
Kirkland had far less to do than his opposite number but kept out a low free-kick from Smertin in the first minute and then made a double save in the 76th minute to deny Hughes a second goal after he had dropped a centre at the midfielder's feet.
Liverpool piled on the pressure in the last couple of minutes and Jamie Carragher almost levelled with a header but with Hislop in commanding form Pompey held on to inflict more misery on Gerard Houllier.