Until that moment the Azzurri looked to be heading for a frustrating night and the need for another point to secure their path to Poland and Ukraine. But a defensive mix-up between Marko Suler and Bostjan Cesar left Pazzini to smash home from five yards.
They now have an unassailable lead atop qualifying Group C despite Serbia's win over the Faroe Islands. But the three points will do little to paper over the cracks of another largely uninspiring performance against poor opponents, in which Italy should have sealed victory long before Pazzini's goal.
Just as they had done in the Faroes on Friday, Italy started at breakneck speed, creating their first chance within 60 seconds as Giuseppe Rossi beat a dawdling backline only for Jasmin Handanovic to save his powerful shot with his feet. Playing in his home stadium, Riccardo Montolivo ghosted into the box to drift a header wide from Federico Balzaretti's cross and then Daniele De Rossi latched onto Montolivo's pass but shanked his effort wide. All that was within the first six minutes.
Rossi screwed wide after being set up by Antonio Cassano following more good play from Montolivo and then Thiago Motta failed to get significant purchase on his shot from Cassano's chip over the top. Italy's worst miss came from De Rossi as he somehow failed to turn in Montolivo's centre from two yards out with the goal at his mercy.
The defensive Slovenians created little, but did twice bring Italy goalkeeper Gianluigi Buffon into the game from fierce strikes by Dare Vrsic and Robert Koren. Italy may have created many chances in the first period but after the break they started looking increasingly laboured. That prompted coach Cesare Prandelli to take off Cassano and send on a more direct forward in Pazzini.
The hosts finally burst into life midway through the half as De Rossi was denied twice in quick succession, first in an almighty goalmouth scramble and then from close range from a right-wing cross.
Slovenia then showed their limitations on a counter-attack that should have garnered a one-on-one with Buffon, but instead Andraz Kirm's pass was a touch under-hit and Josip Ilicic missed the ball completely as he tried to check his run. They had another sight of the Italy goal on the counter but substitute Nejc Pecnik's shot was deflected over.
But the visitors then almost committed suicide with Suler's awful backpass producing an even worse attempt to control from Handanovic who then had to make a sliding tackle to deny Pazzini an open goal. Moments later, though, Suler and Cesar collided five minutes from time to present Pazzini with the chance to be the home hero.